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Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]2<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title></title><link rel="stylesheet" type="text/css" href="docbook-xsl.css"><meta name="generator" content="DocBook XSL Stylesheets V1.76.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div lang="en" class="book"><div class="titlepage"><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="part"><a href="#_git_user_manual">I. Git User Manual</a></span></dt><dd><dl><dt><span class="chapter"><a href="#repositories-and-branches">1. Repositories and Branches</a></span></dt><dd><dl><dt><span class="section"><a href="#how-to-get-a-git-repository">How to get a Git repository</a></span></dt><dt><span class="section"><a href="#how-to-check-out">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#understanding-commits">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#manipulating-branches">Manipulating branches</a></span></dt><dt><span class="section"><a href="#detached-head">Examining an old version without creating a new branch</a></span></dt><dt><span class="section"><a href="#examining-remote-branches">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-With-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#fetching-branches">Fetching branches from other repositories</a></span></dt></dl></dd><dt><span class="chapter"><a href="#exploring-git-history">2. Exploring Git history</a></span></dt><dd><dl><dt><span class="section"><a href="#using-bisect">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#naming-commits">Naming commits</a></span></dt><dt><span class="section"><a href="#creating-tags">Creating tags</a></span></dt><dt><span class="section"><a href="#browsing-revisions">Browsing revisions</a></span></dt><dt><span class="section"><a href="#generating-diffs">Generating diffs</a></span></dt><dt><span class="section"><a href="#viewing-old-file-versions">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#history-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#Developing-With-git">3. Developing with Git</a></span></dt><dd><dl><dt><span class="section"><a href="#telling-git-your-name">Telling Git your name</a></span></dt><dt><span class="section"><a href="#creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">How to make a commit</a></span></dt><dt><span class="section"><a href="#creating-good-commit-messages">Creating good commit messages</a></span></dt><dt><span class="section"><a href="#ignoring-files">Ignoring files</a></span></dt><dt><span class="section"><a href="#how-to-merge">How to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="section"><a href="#undoing-a-merge">Undoing a merge</a></span></dt><dt><span class="section"><a href="#fast-forwards">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#fixing-mistakes">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="section"><a href="#ensuring-good-performance">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#ensuring-reliability">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#sharing-development">4. Sharing development with others</a></span></dt><dd><dl><dt><span class="section"><a href="#getting-updates-With-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#submitting-patches">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#importing-patches">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#public-repositories">Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="section"><a href="#sharing-development-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#cleaning-up-history">5. Rewriting history and maintaining patch series</a></span></dt><dd><dl><dt><span class="section"><a href="#patch-series">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#using-git-rebase">Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="section"><a href="#rewriting-one-commit">Rewriting a single commit</a></span></dt><dt><span class="section"><a href="#reordering-patch-series">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#interactive-rebase">Using interactive rebases</a></span></dt><dt><span class="section"><a href="#patch-series-tools">Other tools</a></span></dt><dt><span class="section"><a href="#problems-With-rewriting-history">Problems with rewriting history</a></span></dt><dt><span class="section"><a href="#bisect-merges">Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></dd><dt><span class="chapter"><a href="#advanced-branch-management">6. Advanced branch management</a></span></dt><dd><dl><dt><span class="section"><a href="#fetching-individual-branches">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fetch-fast-forwards">git fetch and fast-forwards</a></span></dt><dt><span class="section"><a href="#forcing-fetch">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#remote-branch-configuration">Configuring remote-tracking branches</a></span></dt></dl></dd><dt><span class="chapter"><a href="#git-concepts">7. Git concepts</a></span></dt><dd><dl><dt><span class="section"><a href="#the-object-database">The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="section"><a href="#the-index">The index</a></span></dt></dl></dd><dt><span class="chapter"><a href="#submodules">8. Submodules</a></span></dt><dd><dl><dt><span class="section"><a href="#_pitfalls_with_submodules">Pitfalls with submodules</a></span></dt></dl></dd><dt><span class="chapter"><a href="#low-level-operations">9. Low-level Git operations</a></span></dt><dd><dl><dt><span class="section"><a href="#object-manipulation">Object access and manipulation</a></span></dt><dt><span class="section"><a href="#the-workflow">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#examining-the-data">Examining the data</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees-2">Merging multiple trees, continued</a></span></dt></dl></dd><dt><span class="chapter"><a href="#hacking-git">10. Hacking Git</a></span></dt><dd><dl><dt><span class="section"><a href="#object-details">Object storage format</a></span></dt><dt><span class="section"><a href="#birdview-on-the-source-code">A birds-eye view of Git’s source code</a></span></dt></dl></dd><dt><span class="chapter"><a href="#glossary">11. Git Glossary</a></span></dt><dt><span class="appendix"><a href="#git-quick-start">A. Git Quick Reference</a></span></dt><dd><dl><dt><span class="section"><a href="#quick-creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#managing-branches">Managing branches</a></span></dt><dt><span class="section"><a href="#exploring-history">Exploring history</a></span></dt><dt><span class="section"><a href="#making-changes">Making changes</a></span></dt><dt><span class="section"><a href="#merging">Merging</a></span></dt><dt><span class="section"><a href="#sharing-your-changes">Sharing your changes</a></span></dt><dt><span class="section"><a href="#repository-maintenance">Repository maintenance</a></span></dt></dl></dd><dt><span class="appendix"><a href="#todo">B. Notes and todo list for this manual</a></span></dt></dl></dd></dl></div><div class="part" title="Part I. Git User Manual"><div class="titlepage"><div><div><h1 class="title"><a name="_git_user_manual"></a>Part I. Git User Manual</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="chapter"><a href="#repositories-and-branches">1. Repositories and Branches</a></span></dt><dd><dl><dt><span class="section"><a href="#how-to-get-a-git-repository">How to get a Git repository</a></span></dt><dt><span class="section"><a href="#how-to-check-out">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#understanding-commits">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#manipulating-branches">Manipulating branches</a></span></dt><dt><span class="section"><a href="#detached-head">Examining an old version without creating a new branch</a></span></dt><dt><span class="section"><a href="#examining-remote-branches">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-With-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#fetching-branches">Fetching branches from other repositories</a></span></dt></dl></dd><dt><span class="chapter"><a href="#exploring-git-history">2. Exploring Git history</a></span></dt><dd><dl><dt><span class="section"><a href="#using-bisect">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#naming-commits">Naming commits</a></span></dt><dt><span class="section"><a href="#creating-tags">Creating tags</a></span></dt><dt><span class="section"><a href="#browsing-revisions">Browsing revisions</a></span></dt><dt><span class="section"><a href="#generating-diffs">Generating diffs</a></span></dt><dt><span class="section"><a href="#viewing-old-file-versions">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#history-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#Developing-With-git">3. Developing with Git</a></span></dt><dd><dl><dt><span class="section"><a href="#telling-git-your-name">Telling Git your name</a></span></dt><dt><span class="section"><a href="#creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">How to make a commit</a></span></dt><dt><span class="section"><a href="#creating-good-commit-messages">Creating good commit messages</a></span></dt><dt><span class="section"><a href="#ignoring-files">Ignoring files</a></span></dt><dt><span class="section"><a href="#how-to-merge">How to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="section"><a href="#undoing-a-merge">Undoing a merge</a></span></dt><dt><span class="section"><a href="#fast-forwards">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#fixing-mistakes">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="section"><a href="#ensuring-good-performance">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#ensuring-reliability">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#sharing-development">4. Sharing development with others</a></span></dt><dd><dl><dt><span class="section"><a href="#getting-updates-With-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#submitting-patches">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#importing-patches">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#public-repositories">Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="section"><a href="#sharing-development-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#cleaning-up-history">5. Rewriting history and maintaining patch series</a></span></dt><dd><dl><dt><span class="section"><a href="#patch-series">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#using-git-rebase">Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="section"><a href="#rewriting-one-commit">Rewriting a single commit</a></span></dt><dt><span class="section"><a href="#reordering-patch-series">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#interactive-rebase">Using interactive rebases</a></span></dt><dt><span class="section"><a href="#patch-series-tools">Other tools</a></span></dt><dt><span class="section"><a href="#problems-With-rewriting-history">Problems with rewriting history</a></span></dt><dt><span class="section"><a href="#bisect-merges">Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></dd><dt><span class="chapter"><a href="#advanced-branch-management">6. Advanced branch management</a></span></dt><dd><dl><dt><span class="section"><a href="#fetching-individual-branches">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fetch-fast-forwards">git fetch and fast-forwards</a></span></dt><dt><span class="section"><a href="#forcing-fetch">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#remote-branch-configuration">Configuring remote-tracking branches</a></span></dt></dl></dd><dt><span class="chapter"><a href="#git-concepts">7. Git concepts</a></span></dt><dd><dl><dt><span class="section"><a href="#the-object-database">The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="section"><a href="#the-index">The index</a></span></dt></dl></dd><dt><span class="chapter"><a href="#submodules">8. Submodules</a></span></dt><dd><dl><dt><span class="section"><a href="#_pitfalls_with_submodules">Pitfalls with submodules</a></span></dt></dl></dd><dt><span class="chapter"><a href="#low-level-operations">9. Low-level Git operations</a></span></dt><dd><dl><dt><span class="section"><a href="#object-manipulation">Object access and manipulation</a></span></dt><dt><span class="section"><a href="#the-workflow">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#examining-the-data">Examining the data</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees-2">Merging multiple trees, continued</a></span></dt></dl></dd><dt><span class="chapter"><a href="#hacking-git">10. Hacking Git</a></span></dt><dd><dl><dt><span class="section"><a href="#object-details">Object storage format</a></span></dt><dt><span class="section"><a href="#birdview-on-the-source-code">A birds-eye view of Git’s source code</a></span></dt></dl></dd><dt><span class="chapter"><a href="#glossary">11. Git Glossary</a></span></dt><dt><span class="appendix"><a href="#git-quick-start">A. Git Quick Reference</a></span></dt><dd><dl><dt><span class="section"><a href="#quick-creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#managing-branches">Managing branches</a></span></dt><dt><span class="section"><a href="#exploring-history">Exploring history</a></span></dt><dt><span class="section"><a href="#making-changes">Making changes</a></span></dt><dt><span class="section"><a href="#merging">Merging</a></span></dt><dt><span class="section"><a href="#sharing-your-changes">Sharing your changes</a></span></dt><dt><span class="section"><a href="#repository-maintenance">Repository maintenance</a></span></dt></dl></dd><dt><span class="appendix"><a href="#todo">B. Notes and todo list for this manual</a></span></dt></dl></div><p>Git is a fast distributed revision control system.</p><p>This manual is designed to be readable by someone with basic UNIX
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]3command-line skills, but no previous knowledge of Git.</p><p><a class="xref" href="#repositories-and-branches" title="Chapter 1. Repositories and Branches">Chapter 1, <i>Repositories and Branches</i></a> and <a class="xref" href="#exploring-git-history" title="Chapter 2. Exploring Git history">Chapter 2, <i>Exploring Git history</i></a> explain how
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]4to fetch and study a project using git—read these chapters to learn how
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]5to build and test a particular version of a software project, search for
6regressions, and so on.</p><p>People needing to do actual development will also want to read
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]7<a class="xref" href="#Developing-With-git" title="Chapter 3. Developing with Git">Chapter 3, <i>Developing with Git</i></a> and <a class="xref" href="#sharing-development" title="Chapter 4. Sharing development with others">Chapter 4, <i>Sharing development with others</i></a>.</p><p>Further chapters cover more specialized topics.</p><p>Comprehensive reference documentation is available through the man
Junio C Hamanof66ecee2008-11-17 18:25:43[diff] [blame]8pages, or <a class="ulink" href="git-help.html" target="_top">git-help(1)</a> command. For example, for the command
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]9<code class="literal">git clone &lt;repo&gt;</code>, you can either use:</p><pre class="literallayout">$ man git-clone</pre><p>or:</p><pre class="literallayout">$ git help clone</pre><p>With the latter, you can use the manual viewer of your choice; see
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]10<a class="ulink" href="git-help.html" target="_top">git-help(1)</a> for more information.</p><p>See also <a class="xref" href="#git-quick-start" title="Appendix A. Git Quick Reference">Appendix A, <i>Git Quick Reference</i></a> for a brief overview of Git commands,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]11without any explanation.</p><p>Finally, see <a class="xref" href="#todo" title="Appendix B. Notes and todo list for this manual">Appendix B, <i>Notes and todo list for this manual</i></a> for ways that you can help make this manual more
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]12complete.</p><div class="chapter" title="Chapter 1. Repositories and Branches"><div class="titlepage"><div><div><h2 class="title"><a name="repositories-and-branches"></a>Chapter 1. Repositories and Branches</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#how-to-get-a-git-repository">How to get a Git repository</a></span></dt><dt><span class="section"><a href="#how-to-check-out">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#understanding-commits">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#manipulating-branches">Manipulating branches</a></span></dt><dt><span class="section"><a href="#detached-head">Examining an old version without creating a new branch</a></span></dt><dt><span class="section"><a href="#examining-remote-branches">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-With-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#fetching-branches">Fetching branches from other repositories</a></span></dt></dl></div><div class="section" title="How to get a Git repository"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-get-a-git-repository"></a>How to get a Git repository</h2></div></div></div><p>It will be useful to have a Git repository to experiment with as you
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]13read this manual.</p><p>The best way to get one is by using the <a class="ulink" href="git-clone.html" target="_top">git-clone(1)</a> command to
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]14download a copy of an existing repository. If you don’t already have a
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]15project in mind, here are some interesting examples:</p><pre class="literallayout"> # Git itself (approx. 40MB download):
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]16$ git clone git://git.kernel.org/pub/scm/git/git.git
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]17 # the Linux kernel (approx. 640MB download):
18$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git</pre><p>The initial clone may be time-consuming for a large project, but you
Junio C Hamanoa1952302013-07-01 21:31:18[diff] [blame]19will only need to clone once.</p><p>The clone command creates a new directory named after the project
20(<code class="literal">git</code> or <code class="literal">linux</code> in the examples above). After you cd into this
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]21directory, you will see that it contains a copy of the project files,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]22called the <a class="link" href="#def_working_tree">working tree</a>, together with a special
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]23top-level directory named <code class="literal">.git</code>, which contains all the information
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]24about the history of the project.</p></div><div class="section" title="How to check out a different version of a project"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-check-out"></a>How to check out a different version of a project</h2></div></div></div><p>Git is best thought of as a tool for storing the history of a collection
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]25of files. It stores the history as a compressed collection of
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]26interrelated snapshots of the project’s contents. In Git each such
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]27version is called a <a class="link" href="#def_commit">commit</a>.</p><p>Those snapshots aren’t necessarily all arranged in a single line from
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]28oldest to newest; instead, work may simultaneously proceed along
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]29parallel lines of development, called <a class="link" href="#def_branch">branches</a>, which may
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]30merge and diverge.</p><p>A single Git repository can track development on multiple branches. It
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]31does this by keeping a list of <a class="link" href="#def_head">heads</a> which reference the
32latest commit on each branch; the <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a> command shows
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]33you the list of branch heads:</p><pre class="literallayout">$ git branch
34* master</pre><p>A freshly cloned repository contains a single branch head, by default
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]35named "master", with the working directory initialized to the state of
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]36the project referred to by that branch head.</p><p>Most projects also use <a class="link" href="#def_tag">tags</a>. Tags, like heads, are
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]37references into the project’s history, and can be listed using the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]38<a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> command:</p><pre class="literallayout">$ git tag -l
39v2.6.11
40v2.6.11-tree
41v2.6.12
42v2.6.12-rc2
43v2.6.12-rc3
44v2.6.12-rc4
45v2.6.12-rc5
46v2.6.12-rc6
47v2.6.13
48...</pre><p>Tags are expected to always point at the same version of a project,
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]49while heads are expected to advance as development progresses.</p><p>Create a new branch head pointing to one of these versions and check it
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]50out using <a class="ulink" href="git-checkout.html" target="_top">git-checkout(1)</a>:</p><pre class="literallayout">$ git checkout -b new v2.6.13</pre><p>The working directory then reflects the contents that the project had
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]51when it was tagged v2.6.13, and <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a> shows two
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]52branches, with an asterisk marking the currently checked-out branch:</p><pre class="literallayout">$ git branch
53 master
54* new</pre><p>If you decide that you’d rather see version 2.6.17, you can modify
55the current branch to point at v2.6.17 instead, with</p><pre class="literallayout">$ git reset --hard v2.6.17</pre><p>Note that if the current branch head was your only reference to a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]56particular point in history, then resetting that branch may leave you
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]57with no way to find the history it used to point to; so use this command
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]58carefully.</p></div><div class="section" title="Understanding History: Commits"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="understanding-commits"></a>Understanding History: Commits</h2></div></div></div><p>Every change in the history of a project is represented by a commit.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]59The <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> command shows the most recent commit on the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]60current branch:</p><pre class="literallayout">$ git show
61commit 17cf781661e6d38f737f15f53ab552f1e95960d7
62Author: Linus Torvalds &lt;torvalds@ppc970.osdl.org.(none)&gt;
63Date: Tue Apr 19 14:11:06 2005 -0700
64
65 Remove duplicate getenv(DB_ENVIRONMENT) call
66
67 Noted by Tony Luck.
68
69diff --git a/init-db.c b/init-db.c
70index 65898fa..b002dc6 100644
71--- a/init-db.c
72+++ b/init-db.c
73@@ -7,7 +7,7 @@
74
75 int main(int argc, char **argv)
76 {
77- char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
78+ char *sha1_dir, *path;
79 int len, i;
80
81 if (mkdir(".git", 0755) &lt; 0) {</pre><p>As you can see, a commit shows who made the latest change, what they
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]82did, and why.</p><p>Every commit has a 40-hexdigit id, sometimes called the "object name" or the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]83"SHA-1 id", shown on the first line of the <code class="literal">git show</code> output. You can usually
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]84refer to a commit by a shorter name, such as a tag or a branch name, but this
85longer name can also be useful. Most importantly, it is a globally unique
86name for this commit: so if you tell somebody else the object name (for
87example in email), then you are guaranteed that name will refer to the same
88commit in their repository that it does in yours (assuming their repository
89has that commit at all). Since the object name is computed as a hash over the
90contents of the commit, you are guaranteed that the commit can never change
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]91without its name also changing.</p><p>In fact, in <a class="xref" href="#git-concepts" title="Chapter 7. Git concepts">Chapter 7, <i>Git concepts</i></a> we shall see that everything stored in Git
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]92history, including file data and directory contents, is stored in an object
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]93with a name that is a hash of its contents.</p><div class="section" title="Understanding history: commits, parents, and reachability"><div class="titlepage"><div><div><h3 class="title"><a name="understanding-reachability"></a>Understanding history: commits, parents, and reachability</h3></div></div></div><p>Every commit (except the very first commit in a project) also has a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]94parent commit which shows what happened before this commit.
95Following the chain of parents will eventually take you back to the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]96beginning of the project.</p><p>However, the commits do not form a simple list; Git allows lines of
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]97development to diverge and then reconverge, and the point where two
98lines of development reconverge is called a "merge". The commit
99representing a merge can therefore have more than one parent, with
100each parent representing the most recent commit on one of the lines
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]101of development leading to that point.</p><p>The best way to see how this works is using the <a class="ulink" href="gitk.html" target="_top">gitk(1)</a>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]102command; running gitk now on a Git repository and looking for merge
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]103commits will help understand how Git organizes history.</p><p>In the following, we say that commit X is "reachable" from commit Y
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]104if commit X is an ancestor of commit Y. Equivalently, you could say
Junio C Hamanoa6387422007-08-25 03:54:27[diff] [blame]105that Y is a descendant of X, or that there is a chain of parents
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]106leading from commit Y to commit X.</p></div><div class="section" title="Understanding history: History diagrams"><div class="titlepage"><div><div><h3 class="title"><a name="history-diagrams"></a>Understanding history: History diagrams</h3></div></div></div><p>We will sometimes represent Git history using diagrams like the one
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]107below. Commits are shown as "o", and the links between them with
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]108lines drawn with - / and \. Time goes left to right:</p><pre class="literallayout"> o--o--o &lt;-- Branch A
109 /
110 o--o--o &lt;-- master
111 \
112 o--o--o &lt;-- Branch B</pre><p>If we need to talk about a particular commit, the character "o" may
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]113be replaced with another letter or number.</p></div><div class="section" title="Understanding history: What is a branch?"><div class="titlepage"><div><div><h3 class="title"><a name="what-is-a-branch"></a>Understanding history: What is a branch?</h3></div></div></div><p>When we need to be precise, we will use the word "branch" to mean a line
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]114of development, and "branch head" (or just "head") to mean a reference
115to the most recent commit on a branch. In the example above, the branch
116head named "A" is a pointer to one particular commit, but we refer to
117the line of three commits leading up to that point as all being part of
118"branch A".</p><p>However, when no confusion will result, we often just use the term
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]119"branch" both for branches and for branch heads.</p></div></div><div class="section" title="Manipulating branches"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="manipulating-branches"></a>Manipulating branches</h2></div></div></div><p>Creating, deleting, and modifying branches is quick and easy; here’s
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]120a summary of the commands:</p><div class="variablelist"><dl><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]121<code class="literal">git branch</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]122</span></dt><dd>
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]123 list all branches.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]124</dd><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]125<code class="literal">git branch &lt;branch&gt;</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]126</span></dt><dd>
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]127 create a new branch named <code class="literal">&lt;branch&gt;</code>, referencing the same
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]128 point in history as the current branch.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]129</dd><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]130<code class="literal">git branch &lt;branch&gt; &lt;start-point&gt;</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]131</span></dt><dd>
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]132 create a new branch named <code class="literal">&lt;branch&gt;</code>, referencing
133 <code class="literal">&lt;start-point&gt;</code>, which may be specified any way you like,
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]134 including using a branch name or a tag name.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]135</dd><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]136<code class="literal">git branch -d &lt;branch&gt;</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]137</span></dt><dd>
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]138 delete the branch <code class="literal">&lt;branch&gt;</code>; if the branch is not fully
139 merged in its upstream branch or contained in the current branch,
140 this command will fail with a warning.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]141</dd><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]142<code class="literal">git branch -D &lt;branch&gt;</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]143</span></dt><dd>
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]144 delete the branch <code class="literal">&lt;branch&gt;</code> irrespective of its merged status.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]145</dd><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]146<code class="literal">git checkout &lt;branch&gt;</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]147</span></dt><dd>
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]148 make the current branch <code class="literal">&lt;branch&gt;</code>, updating the working
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]149 directory to reflect the version referenced by <code class="literal">&lt;branch&gt;</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]150</dd><dt><span class="term">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]151<code class="literal">git checkout -b &lt;new&gt; &lt;start-point&gt;</code>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]152</span></dt><dd>
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]153 create a new branch <code class="literal">&lt;new&gt;</code> referencing <code class="literal">&lt;start-point&gt;</code>, and
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]154 check it out.
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]155</dd></dl></div><p>The special symbol "HEAD" can always be used to refer to the current
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]156branch. In fact, Git uses a file named <code class="literal">HEAD</code> in the <code class="literal">.git</code> directory
157to remember which branch is current:</p><pre class="literallayout">$ cat .git/HEAD
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]158ref: refs/heads/master</pre></div><div class="section" title="Examining an old version without creating a new branch"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="detached-head"></a>Examining an old version without creating a new branch</h2></div></div></div><p>The <code class="literal">git checkout</code> command normally expects a branch head, but will also
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]159accept an arbitrary commit; for example, you can check out the commit
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]160referenced by a tag:</p><pre class="literallayout">$ git checkout v2.6.17
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]161Note: checking out 'v2.6.17'.
162
163You are in 'detached HEAD' state. You can look around, make experimental
164changes and commit them, and you can discard any commits you make in this
165state without impacting any branches by performing another checkout.
166
167If you want to create a new branch to retain commits you create, you may
168do so (now or later) by using -b with the checkout command again. Example:
169
170 git checkout -b new_branch_name
171
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]172HEAD is now at 427abfa... Linux v2.6.17</pre><p>The HEAD then refers to the SHA-1 of the commit instead of to a branch,
173and git branch shows that you are no longer on a branch:</p><pre class="literallayout">$ cat .git/HEAD
174427abfa28afedffadfca9dd8b067eb6d36bac53f
175$ git branch
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]176* (detached from v2.6.17)
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]177 master</pre><p>In this case we say that the HEAD is "detached".</p><p>This is an easy way to check out a particular version without having to
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]178make up a name for the new branch. You can still create a new branch
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]179(or tag) for this version later if you decide to.</p></div><div class="section" title="Examining branches from a remote repository"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="examining-remote-branches"></a>Examining branches from a remote repository</h2></div></div></div><p>The "master" branch that was created at the time you cloned is a copy
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]180of the HEAD in the repository that you cloned from. That repository
181may also have had other branches, though, and your local repository
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]182keeps branches which track each of those remote branches, called
183remote-tracking branches, which you
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]184can view using the <code class="literal">-r</code> option to <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a>:</p><pre class="literallayout">$ git branch -r
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]185 origin/HEAD
186 origin/html
187 origin/maint
188 origin/man
189 origin/master
190 origin/next
191 origin/pu
192 origin/todo</pre><p>In this example, "origin" is called a remote repository, or "remote"
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]193for short. The branches of this repository are called "remote
194branches" from our point of view. The remote-tracking branches listed
195above were created based on the remote branches at clone time and will
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]196be updated by <code class="literal">git fetch</code> (hence <code class="literal">git pull</code>) and <code class="literal">git push</code>. See
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]197<a class="xref" href="#Updating-a-repository-With-git-fetch" title="Updating a repository with git fetch">the section called “Updating a repository with git fetch”</a> for details.</p><p>You might want to build on one of these remote-tracking branches
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]198on a branch of your own, just as you would for a tag:</p><pre class="literallayout">$ git checkout -b my-todo-copy origin/todo</pre><p>You can also check out <code class="literal">origin/todo</code> directly to examine it or
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]199write a one-off patch. See <a class="link" href="#detached-head" title="Examining an old version without creating a new branch">detached head</a>.</p><p>Note that the name "origin" is just the name that Git uses by default
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]200to refer to the repository that you cloned from.</p></div><div class="section" title="Naming branches, tags, and other references"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-git-stores-references"></a>Naming branches, tags, and other references</h2></div></div></div><p>Branches, remote-tracking branches, and tags are all references to
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]201commits. All references are named with a slash-separated path name
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]202starting with <code class="literal">refs</code>; the names we’ve been using so far are actually
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]203shorthand:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]204The branch <code class="literal">test</code> is short for <code class="literal">refs/heads/test</code>.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]205</li><li class="listitem">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]206The tag <code class="literal">v2.6.18</code> is short for <code class="literal">refs/tags/v2.6.18</code>.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]207</li><li class="listitem">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]208<code class="literal">origin/master</code> is short for <code class="literal">refs/remotes/origin/master</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]209</li></ul></div><p>The full name is occasionally useful if, for example, there ever
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]210exists a tag and a branch with the same name.</p><p>(Newly created refs are actually stored in the <code class="literal">.git/refs</code> directory,
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]211under the path given by their name. However, for efficiency reasons
212they may also be packed together in a single file; see
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]213<a class="ulink" href="git-pack-refs.html" target="_top">git-pack-refs(1)</a>).</p><p>As another useful shortcut, the "HEAD" of a repository can be referred
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]214to just using the name of that repository. So, for example, "origin"
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]215is usually a shortcut for the HEAD branch in the repository "origin".</p><p>For the complete list of paths which Git checks for references, and
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]216the order it uses to decide which to choose when there are multiple
217references with the same shorthand name, see the "SPECIFYING
Junio C Hamanoc27b7332010-10-14 04:37:28[diff] [blame]218REVISIONS" section of <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a>.</p></div><div class="section" title="Updating a repository with git fetch"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="Updating-a-repository-With-git-fetch"></a>Updating a repository with git fetch</h2></div></div></div><p>Eventually the developer cloned from will do additional work in her
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]219repository, creating new commits and advancing the branches to point
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]220at the new commits.</p><p>The command <code class="literal">git fetch</code>, with no arguments, will update all of the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]221remote-tracking branches to the latest version found in her
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]222repository. It will not touch any of your own branches—not even the
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]223"master" branch that was created for you on clone.</p></div><div class="section" title="Fetching branches from other repositories"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fetching-branches"></a>Fetching branches from other repositories</h2></div></div></div><p>You can also track branches from repositories other than the one you
Junio C Hamanoa1952302013-07-01 21:31:18[diff] [blame]224cloned from, using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>:</p><pre class="literallayout">$ git remote add staging git://git.kernel.org/.../gregkh/staging.git
225$ git fetch staging
226...
227From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
228 * [new branch] master -&gt; staging/master
229 * [new branch] staging-linus -&gt; staging/staging-linus
230 * [new branch] staging-next -&gt; staging/staging-next</pre><p>New remote-tracking branches will be stored under the shorthand name
231that you gave <code class="literal">git remote add</code>, in this case <code class="literal">staging</code>:</p><pre class="literallayout">$ git branch -r
232 origin/HEAD -&gt; origin/master
233 origin/master
234 staging/master
235 staging/staging-linus
236 staging/staging-next</pre><p>If you run <code class="literal">git fetch &lt;remote&gt;</code> later, the remote-tracking branches
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]237for the named <code class="literal">&lt;remote&gt;</code> will be updated.</p><p>If you examine the file <code class="literal">.git/config</code>, you will see that Git has added
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]238a new stanza:</p><pre class="literallayout">$ cat .git/config
239...
Junio C Hamanoa1952302013-07-01 21:31:18[diff] [blame]240[remote "staging"]
241 url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
242 fetch = +refs/heads/*:refs/remotes/staging/*
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]243...</pre><p>This is what causes Git to track the remote’s branches; you may modify
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]244or delete these configuration options by editing <code class="literal">.git/config</code> with a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]245text editor. (See the "CONFIGURATION FILE" section of
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]246<a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.)</p></div></div><div class="chapter" title="Chapter 2. Exploring Git history"><div class="titlepage"><div><div><h2 class="title"><a name="exploring-git-history"></a>Chapter 2. Exploring Git history</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#using-bisect">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#naming-commits">Naming commits</a></span></dt><dt><span class="section"><a href="#creating-tags">Creating tags</a></span></dt><dt><span class="section"><a href="#browsing-revisions">Browsing revisions</a></span></dt><dt><span class="section"><a href="#generating-diffs">Generating diffs</a></span></dt><dt><span class="section"><a href="#viewing-old-file-versions">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#history-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></div><p>Git is best thought of as a tool for storing the history of a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]247collection of files. It does this by storing compressed snapshots of
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]248the contents of a file hierarchy, together with "commits" which show
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]249the relationships between these snapshots.</p><p>Git provides extremely flexible and fast tools for exploring the
Junio C Hamano39381a72007-02-02 07:35:15[diff] [blame]250history of a project.</p><p>We start with one specialized tool that is useful for finding the
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]251commit that introduced a bug into a project.</p><div class="section" title="How to use bisect to find a regression"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="using-bisect"></a>How to use bisect to find a regression</h2></div></div></div><p>Suppose version 2.6.18 of your project worked, but the version at
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]252"master" crashes. Sometimes the best way to find the cause of such a
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]253regression is to perform a brute-force search through the project’s
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]254history to find the particular commit that caused the problem. The
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]255<a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> command can help you do this:</p><pre class="literallayout">$ git bisect start
256$ git bisect good v2.6.18
257$ git bisect bad master
258Bisecting: 3537 revisions left to test after this
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]259[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]</pre><p>If you run <code class="literal">git branch</code> at this point, you’ll see that Git has
Junio C Hamano9e395072008-07-31 22:11:21[diff] [blame]260temporarily moved you in "(no branch)". HEAD is now detached from any
261branch and points directly to a commit (with commit id 65934…) that
262is reachable from "master" but not from v2.6.18. Compile and test it,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]263and see whether it crashes. Assume it does crash. Then:</p><pre class="literallayout">$ git bisect bad
264Bisecting: 1769 revisions left to test after this
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]265[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings</pre><p>checks out an older version. Continue like this, telling Git at each
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]266stage whether the version it gives you is good or bad, and notice
267that the number of revisions left to test is cut approximately in
268half each time.</p><p>After about 13 tests (in this case), it will output the commit id of
269the guilty commit. You can then examine the commit with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]270<a class="ulink" href="git-show.html" target="_top">git-show(1)</a>, find out who wrote it, and mail them your bug
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]271report with the commit id. Finally, run</p><pre class="literallayout">$ git bisect reset</pre><p>to return you to the branch you were on before.</p><p>Note that the version which <code class="literal">git bisect</code> checks out for you at each
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]272point is just a suggestion, and you’re free to try a different
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]273version if you think it would be a good idea. For example,
274occasionally you may land on a commit that broke something unrelated;
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]275run</p><pre class="literallayout">$ git bisect visualize</pre><p>which will run gitk and label the commit it chose with a marker that
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]276says "bisect". Choose a safe-looking commit nearby, note its commit
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]277id, and check it out with:</p><pre class="literallayout">$ git reset --hard fb47ddb2db...</pre><p>then test, run <code class="literal">bisect good</code> or <code class="literal">bisect bad</code> as appropriate, and
278continue.</p><p>Instead of <code class="literal">git bisect visualize</code> and then <code class="literal">git reset --hard
279fb47ddb2db...</code>, you might just want to tell Git that you want to skip
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]280the current commit:</p><pre class="literallayout">$ git bisect skip</pre><p>In this case, though, Git may not eventually be able to tell the first
Junio C Hamano610d1762008-11-28 06:27:13[diff] [blame]281bad one between some first skipped commits and a later bad commit.</p><p>There are also ways to automate the bisecting process if you have a
Junio C Hamano9e395072008-07-31 22:11:21[diff] [blame]282test script that can tell a good from a bad commit. See
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]283<a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> for more information about this and other <code class="literal">git
284bisect</code> features.</p></div><div class="section" title="Naming commits"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="naming-commits"></a>Naming commits</h2></div></div></div><p>We have seen several ways of naming commits already:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]28540-hexdigit object name
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]286</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]287branch name: refers to the commit at the head of the given
288 branch
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]289</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]290tag name: refers to the commit pointed to by the given tag
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]291 (we’ve seen branches and tags are special cases of
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]292 <a class="link" href="#how-git-stores-references" title="Naming branches, tags, and other references">references</a>).
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]293</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]294HEAD: refers to the head of the current branch
295</li></ul></div><p>There are many more; see the "SPECIFYING REVISIONS" section of the
Junio C Hamanoc27b7332010-10-14 04:37:28[diff] [blame]296<a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> man page for the complete list of ways to
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]297name revisions. Some examples:</p><pre class="literallayout">$ git show fb47ddb2 # the first few characters of the object name
298 # are usually enough to specify it uniquely
299$ git show HEAD^ # the parent of the HEAD commit
300$ git show HEAD^^ # the grandparent
301$ git show HEAD~4 # the great-great-grandparent</pre><p>Recall that merge commits may have more than one parent; by default,
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]302<code class="literal">^</code> and <code class="literal">~</code> follow the first parent listed in the commit, but you can
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]303also choose:</p><pre class="literallayout">$ git show HEAD^1 # show the first parent of HEAD
304$ git show HEAD^2 # show the second parent of HEAD</pre><p>In addition to HEAD, there are several other special names for
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]305commits:</p><p>Merges (to be discussed later), as well as operations such as
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]306<code class="literal">git reset</code>, which change the currently checked-out commit, generally
307set ORIG_HEAD to the value HEAD had before the current operation.</p><p>The <code class="literal">git fetch</code> operation always stores the head of the last fetched
308branch in FETCH_HEAD. For example, if you run <code class="literal">git fetch</code> without
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]309specifying a local branch as the target of the operation</p><pre class="literallayout">$ git fetch git://example.com/proj.git theirbranch</pre><p>the fetched commits will still be available from FETCH_HEAD.</p><p>When we discuss merges we’ll also see the special name MERGE_HEAD,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]310which refers to the other branch that we’re merging in to the current
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]311branch.</p><p>The <a class="ulink" href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> command is a low-level command that is
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]312occasionally useful for translating some name for a commit to the object
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]313name for that commit:</p><pre class="literallayout">$ git rev-parse origin
314e05db0fd4f31dde7005f075a84f96b360d05984b</pre></div><div class="section" title="Creating tags"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-tags"></a>Creating tags</h2></div></div></div><p>We can also create a tag to refer to a particular commit; after
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]315running</p><pre class="literallayout">$ git tag stable-1 1b2e1d63ff</pre><p>You can use <code class="literal">stable-1</code> to refer to the commit 1b2e1d63ff.</p><p>This creates a "lightweight" tag. If you would also like to include a
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]316comment with the tag, and possibly sign it cryptographically, then you
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]317should create a tag object instead; see the <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> man page
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]318for details.</p></div><div class="section" title="Browsing revisions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="browsing-revisions"></a>Browsing revisions</h2></div></div></div><p>The <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> command can show lists of commits. On its
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]319own, it shows all commits reachable from the parent commit; but you
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]320can also make more specific requests:</p><pre class="literallayout">$ git log v2.5.. # commits since (not reachable from) v2.5
321$ git log test..master # commits reachable from master but not test
322$ git log master..test # ...reachable from test but not master
323$ git log master...test # ...reachable from either test or master,
324 # but not both
325$ git log --since="2 weeks ago" # commits from the last 2 weeks
326$ git log Makefile # commits which modify Makefile
327$ git log fs/ # ... which modify any file under fs/
328$ git log -S'foo()' # commits which add or remove any file data
329 # matching the string 'foo()'</pre><p>And of course you can combine all of these; the following finds
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]330commits since v2.5 which touch the <code class="literal">Makefile</code> or any file under <code class="literal">fs</code>:</p><pre class="literallayout">$ git log v2.5.. Makefile fs/</pre><p>You can also ask git log to show patches:</p><pre class="literallayout">$ git log -p</pre><p>See the <code class="literal">--pretty</code> option in the <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> man page for more
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]331display options.</p><p>Note that git log starts with the most recent commit and works
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]332backwards through the parents; however, since Git history can contain
Junio C Hamanoee1e4282007-02-04 08:32:04[diff] [blame]333multiple independent lines of development, the particular order that
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]334commits are listed in may be somewhat arbitrary.</p></div><div class="section" title="Generating diffs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="generating-diffs"></a>Generating diffs</h2></div></div></div><p>You can generate diffs between any two versions using
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]335<a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>:</p><pre class="literallayout">$ git diff master..test</pre><p>That will produce the diff between the tips of the two branches. If
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]336you’d prefer to find the diff from their common ancestor to test, you
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]337can use three dots instead of two:</p><pre class="literallayout">$ git diff master...test</pre><p>Sometimes what you want instead is a set of patches; for this you can
338use <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a>:</p><pre class="literallayout">$ git format-patch master..test</pre><p>will generate a file with a patch for each commit reachable from test
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]339but not from master.</p></div><div class="section" title="Viewing old file versions"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="viewing-old-file-versions"></a>Viewing old file versions</h2></div></div></div><p>You can always view an old version of a file by just checking out the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]340correct revision first. But sometimes it is more convenient to be
341able to view an old version of a single file without checking
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]342anything out; this command does that:</p><pre class="literallayout">$ git show v2.5:fs/locks.c</pre><p>Before the colon may be anything that names a commit, and after it
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]343may be any path to a file tracked by Git.</p></div><div class="section" title="Examples"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="history-examples"></a>Examples</h2></div></div></div><div class="section" title="Counting the number of commits on a branch"><div class="titlepage"><div><div><h3 class="title"><a name="counting-commits-on-a-branch"></a>Counting the number of commits on a branch</h3></div></div></div><p>Suppose you want to know how many commits you’ve made on <code class="literal">mybranch</code>
344since it diverged from <code class="literal">origin</code>:</p><pre class="literallayout">$ git log --pretty=oneline origin..mybranch | wc -l</pre><p>Alternatively, you may often see this sort of thing done with the
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]345lower-level command <a class="ulink" href="git-rev-list.html" target="_top">git-rev-list(1)</a>, which just lists the SHA-1’s
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]346of all the given commits:</p><pre class="literallayout">$ git rev-list origin..mybranch | wc -l</pre></div><div class="section" title="Check whether two branches point at the same history"><div class="titlepage"><div><div><h3 class="title"><a name="checking-for-equal-branches"></a>Check whether two branches point at the same history</h3></div></div></div><p>Suppose you want to check whether two branches point at the same point
347in history.</p><pre class="literallayout">$ git diff origin..master</pre><p>will tell you whether the contents of the project are the same at the
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]348two branches; in theory, however, it’s possible that the same project
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]349contents could have been arrived at by two different historical
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]350routes. You could compare the object names:</p><pre class="literallayout">$ git rev-list origin
351e05db0fd4f31dde7005f075a84f96b360d05984b
352$ git rev-list master
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]353e05db0fd4f31dde7005f075a84f96b360d05984b</pre><p>Or you could recall that the <code class="literal">...</code> operator selects all commits
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]354reachable from either one reference or the other but not
Junio C Hamano8c5696d2013-02-11 05:35:00[diff] [blame]355both; so</p><pre class="literallayout">$ git log origin...master</pre><p>will return no commits when the two branches are equal.</p></div><div class="section" title="Find first tagged version including a given fix"><div class="titlepage"><div><div><h3 class="title"><a name="finding-tagged-descendants"></a>Find first tagged version including a given fix</h3></div></div></div><p>Suppose you know that the commit e05db0fd fixed a certain problem.
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]356You’d like to find the earliest tagged release that contains that
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]357fix.</p><p>Of course, there may be more than one answer—if the history branched
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]358after commit e05db0fd, then there could be multiple "earliest" tagged
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]359releases.</p><p>You could just visually inspect the commits since e05db0fd:</p><pre class="literallayout">$ gitk e05db0fd..</pre><p>or you can use <a class="ulink" href="git-name-rev.html" target="_top">git-name-rev(1)</a>, which will give the commit a
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]360name based on any tag it finds pointing to one of the commit’s
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]361descendants:</p><pre class="literallayout">$ git name-rev --tags e05db0fd
362e05db0fd tags/v1.5.0-rc1^0~23</pre><p>The <a class="ulink" href="git-describe.html" target="_top">git-describe(1)</a> command does the opposite, naming the
363revision using a tag on which the given commit is based:</p><pre class="literallayout">$ git describe e05db0fd
364v1.5.0-rc0-260-ge05db0f</pre><p>but that may sometimes help you guess which tags might come after the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]365given commit.</p><p>If you just want to verify whether a given tagged version contains a
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]366given commit, you could use <a class="ulink" href="git-merge-base.html" target="_top">git-merge-base(1)</a>:</p><pre class="literallayout">$ git merge-base e05db0fd v1.5.0-rc1
367e05db0fd4f31dde7005f075a84f96b360d05984b</pre><p>The merge-base command finds a common ancestor of the given commits,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]368and always returns one or the other in the case where one is a
369descendant of the other; so the above output shows that e05db0fd
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]370actually is an ancestor of v1.5.0-rc1.</p><p>Alternatively, note that</p><pre class="literallayout">$ git log v1.5.0-rc1..e05db0fd</pre><p>will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]371because it outputs only commits that are not reachable from v1.5.0-rc1.</p><p>As yet another alternative, the <a class="ulink" href="git-show-branch.html" target="_top">git-show-branch(1)</a> command lists
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]372the commits reachable from its arguments with a display on the left-hand
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]373side that indicates which arguments that commit is reachable from.
374So, if you run something like</p><pre class="literallayout">$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]375! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
376available
377 ! [v1.5.0-rc0] GIT v1.5.0 preview
378 ! [v1.5.0-rc1] GIT v1.5.0-rc1
379 ! [v1.5.0-rc2] GIT v1.5.0-rc2
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]380...</pre><p>then a line like</p><pre class="literallayout">+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
381available</pre><p>shows that e05db0fd is reachable from itself, from v1.5.0-rc1,
382and from v1.5.0-rc2, and not from v1.5.0-rc0.</p></div><div class="section" title="Showing commits unique to a given branch"><div class="titlepage"><div><div><h3 class="title"><a name="showing-commits-unique-to-a-branch"></a>Showing commits unique to a given branch</h3></div></div></div><p>Suppose you would like to see all the commits reachable from the branch
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]383head named <code class="literal">master</code> but not from any other head in your repository.</p><p>We can list all the heads in this repository with
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]384<a class="ulink" href="git-show-ref.html" target="_top">git-show-ref(1)</a>:</p><pre class="literallayout">$ git show-ref --heads
385bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial
386db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint
387a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master
38824dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]3891e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes</pre><p>We can get just the branch-head names, and remove <code class="literal">master</code>, with
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]390the help of the standard utilities cut and grep:</p><pre class="literallayout">$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'
391refs/heads/core-tutorial
392refs/heads/maint
393refs/heads/tutorial-2
394refs/heads/tutorial-fixes</pre><p>And then we can ask to see all the commits reachable from master
395but not from these other heads:</p><pre class="literallayout">$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |
396 grep -v '^refs/heads/master' )</pre><p>Obviously, endless variations are possible; for example, to see all
397commits reachable from some head but not from any tag in the repository:</p><pre class="literallayout">$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )</pre><p>(See <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> for explanations of commit-selecting
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]398syntax such as <code class="literal">--not</code>.)</p></div><div class="section" title="Creating a changelog and tarball for a software release"><div class="titlepage"><div><div><h3 class="title"><a name="making-a-release"></a>Creating a changelog and tarball for a software release</h3></div></div></div><p>The <a class="ulink" href="git-archive.html" target="_top">git-archive(1)</a> command can create a tar or zip archive from
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]399any version of a project; for example:</p><pre class="literallayout">$ git archive -o latest.tar.gz --prefix=project/ HEAD</pre><p>will use HEAD to produce a gzipped tar archive in which each filename
400is preceded by <code class="literal">project/</code>. The output file format is inferred from
401the output file extension if possible, see <a class="ulink" href="git-archive.html" target="_top">git-archive(1)</a> for
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]402details.</p><p>Versions of Git older than 1.7.7 don’t know about the <code class="literal">tar.gz</code> format,
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]403you’ll need to use gzip explicitly:</p><pre class="literallayout">$ git archive --format=tar --prefix=project/ HEAD | gzip &gt;latest.tar.gz</pre><p>If you’re releasing a new version of a software project, you may want
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]404to simultaneously make a changelog to include in the release
405announcement.</p><p>Linus Torvalds, for example, makes new kernel releases by tagging them,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]406then running:</p><pre class="literallayout">$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7</pre><p>where release-script is a shell script that looks like:</p><pre class="literallayout">#!/bin/sh
407stable="$1"
408last="$2"
409new="$3"
410echo "# git tag v$new"
411echo "git archive --prefix=linux-$new/ v$new | gzip -9 &gt; ../linux-$new.tar.gz"
412echo "git diff v$stable v$new | gzip -9 &gt; ../patch-$new.gz"
413echo "git log --no-merges v$new ^v$last &gt; ../ChangeLog-$new"
414echo "git shortlog --no-merges v$new ^v$last &gt; ../ShortLog"
415echo "git diff --stat --summary -M v$last v$new &gt; ../diffstat-$new"</pre><p>and then he just cut-and-pastes the output commands after verifying that
Junio C Hamano3b4609d2010-09-30 00:04:34[diff] [blame]416they look OK.</p></div><div class="section" title="Finding commits referencing a file with given content"><div class="titlepage"><div><div><h3 class="title"><a name="Finding-commits-With-given-Content"></a>Finding commits referencing a file with given content</h3></div></div></div><p>Somebody hands you a copy of a file, and asks which commits modified a
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]417file such that it contained the given content either before or after the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]418commit. You can find out with this:</p><pre class="literallayout">$ git log --raw --abbrev=40 --pretty=oneline |
419 grep -B 1 `git hash-object filename`</pre><p>Figuring out why this works is left as an exercise to the (advanced)
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]420student. The <a class="ulink" href="git-log.html" target="_top">git-log(1)</a>, <a class="ulink" href="git-diff-tree.html" target="_top">git-diff-tree(1)</a>, and
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]421<a class="ulink" href="git-hash-object.html" target="_top">git-hash-object(1)</a> man pages may prove helpful.</p></div></div></div><div class="chapter" title="Chapter 3. Developing with Git"><div class="titlepage"><div><div><h2 class="title"><a name="Developing-With-git"></a>Chapter 3. Developing with Git</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#telling-git-your-name">Telling Git your name</a></span></dt><dt><span class="section"><a href="#creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">How to make a commit</a></span></dt><dt><span class="section"><a href="#creating-good-commit-messages">Creating good commit messages</a></span></dt><dt><span class="section"><a href="#ignoring-files">Ignoring files</a></span></dt><dt><span class="section"><a href="#how-to-merge">How to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="section"><a href="#undoing-a-merge">Undoing a merge</a></span></dt><dt><span class="section"><a href="#fast-forwards">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#fixing-mistakes">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="section"><a href="#ensuring-good-performance">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#ensuring-reliability">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt></dl></dd></dl></div><div class="section" title="Telling Git your name"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="telling-git-your-name"></a>Telling Git your name</h2></div></div></div><p>Before creating any commits, you should introduce yourself to Git.
422The easiest way to do so is to use <a class="ulink" href="git-config.html" target="_top">git-config(1)</a>:</p><pre class="literallayout">$ git config --global user.name 'Your Name Comes Here'
423$ git config --global user.email 'you@yourdomain.example.com'</pre><p>Which will add the following to a file named <code class="literal">.gitconfig</code> in your
424home directory:</p><pre class="literallayout">[user]
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]425 name = Your Name Comes Here
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]426 email = you@yourdomain.example.com</pre><p>See the "CONFIGURATION FILE" section of <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for
427details on the configuration file. The file is plain text, so you can
428also edit it with your favorite editor.</p></div><div class="section" title="Creating a new repository"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-a-new-repository"></a>Creating a new repository</h2></div></div></div><p>Creating a new repository from scratch is very easy:</p><pre class="literallayout">$ mkdir project
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]429$ cd project
430$ git init</pre><p>If you have some initial content (say, a tarball):</p><pre class="literallayout">$ tar xzvf project.tar.gz
431$ cd project
432$ git init
433$ git add . # include everything below ./ in the first commit:
434$ git commit</pre></div><div class="section" title="How to make a commit"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-make-a-commit"></a>How to make a commit</h2></div></div></div><p>Creating a new commit takes three steps:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]435Making some changes to the working directory using your
436 favorite editor.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]437</li><li class="listitem">
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]438Telling Git about your changes.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]439</li><li class="listitem">
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]440Creating the commit using the content you told Git about
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]441 in step 2.
442</li></ol></div><p>In practice, you can interleave and repeat steps 1 and 2 as many
443times as you want: in order to keep track of what you want committed
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]444at step 3, Git maintains a snapshot of the tree’s contents in a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]445special staging area called "the index."</p><p>At the beginning, the content of the index will be identical to
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]446that of the HEAD. The command <code class="literal">git diff --cached</code>, which shows
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]447the difference between the HEAD and the index, should therefore
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]448produce no output at that point.</p><p>Modifying the index is easy:</p><p>To update the index with the contents of a new or modified file, use</p><pre class="literallayout">$ git add path/to/file</pre><p>To remove a file from the index and from the working tree, use</p><pre class="literallayout">$ git rm path/to/file</pre><p>After each step you can verify that</p><pre class="literallayout">$ git diff --cached</pre><p>always shows the difference between the HEAD and the index file—this
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]449is what you’d commit if you created the commit now—and that</p><pre class="literallayout">$ git diff</pre><p>shows the difference between the working tree and the index file.</p><p>Note that <code class="literal">git add</code> always adds just the current contents of a file
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]450to the index; further changes to the same file will be ignored unless
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]451you run <code class="literal">git add</code> on the file again.</p><p>When you’re ready, just run</p><pre class="literallayout">$ git commit</pre><p>and Git will prompt you for a commit message and then create the new
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]452commit. Check to make sure it looks like what you expected with</p><pre class="literallayout">$ git show</pre><p>As a special shortcut,</p><pre class="literallayout">$ git commit -a</pre><p>will update the index with any files that you’ve modified or removed
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]453and create a commit, all in one step.</p><p>A number of commands are useful for keeping track of what you’re
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]454about to commit:</p><pre class="literallayout">$ git diff --cached # difference between HEAD and the index; what
455 # would be committed if you ran "commit" now.
456$ git diff # difference between the index file and your
457 # working directory; changes that would not
458 # be included if you ran "commit" now.
459$ git diff HEAD # difference between HEAD and working tree; what
460 # would be committed if you ran "commit -a" now.
461$ git status # a brief per-file summary of the above.</pre><p>You can also use <a class="ulink" href="git-gui.html" target="_top">git-gui(1)</a> to create commits, view changes in
Junio C Hamano4cd1c0e2007-08-06 04:39:14[diff] [blame]462the index and the working tree files, and individually select diff hunks
463for inclusion in the index (by right-clicking on the diff hunk and
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]464choosing "Stage Hunk For Commit").</p></div><div class="section" title="Creating good commit messages"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="creating-good-commit-messages"></a>Creating good commit messages</h2></div></div></div><p>Though not required, it’s a good idea to begin the commit message
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]465with a single short (less than 50 character) line summarizing the
466change, followed by a blank line and then a more thorough
Junio C Hamano281fd392012-09-17 23:57:41[diff] [blame]467description. The text up to the first blank line in a commit
468message is treated as the commit title, and that title is used
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]469throughout Git. For example, <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a> turns a
Junio C Hamano281fd392012-09-17 23:57:41[diff] [blame]470commit into email, and it uses the title on the Subject line and the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]471rest of the commit in the body.</p></div><div class="section" title="Ignoring files"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ignoring-files"></a>Ignoring files</h2></div></div></div><p>A project will often generate files that you do <span class="emphasis"><em>not</em></span> want to track with Git.
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]472This typically includes files generated by a build process or temporary
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]473backup files made by your editor. Of course, <span class="emphasis"><em>not</em></span> tracking files with Git
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]474is just a matter of <span class="emphasis"><em>not</em></span> calling <code class="literal">git add</code> on them. But it quickly becomes
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]475annoying to have these untracked files lying around; e.g. they make
Junio C Hamanoea82cff2009-03-18 01:54:48[diff] [blame]476<code class="literal">git add .</code> practically useless, and they keep showing up in the output of
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]477<code class="literal">git status</code>.</p><p>You can tell Git to ignore certain files by creating a file called
478<code class="literal">.gitignore</code> in the top level of your working directory, with contents
479such as:</p><pre class="literallayout"># Lines starting with '#' are considered comments.
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]480# Ignore any file named foo.txt.
481foo.txt
482# Ignore (generated) html files,
483*.html
484# except foo.html which is maintained by hand.
485!foo.html
486# Ignore objects and archives.
487*.[oa]</pre><p>See <a class="ulink" href="gitignore.html" target="_top">gitignore(5)</a> for a detailed explanation of the syntax. You can
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]488also place .gitignore files in other directories in your working tree, and they
489will apply to those directories and their subdirectories. The <code class="literal">.gitignore</code>
490files can be added to your repository like any other files (just run <code class="literal">git add
491.gitignore</code> and <code class="literal">git commit</code>, as usual), which is convenient when the exclude
492patterns (such as patterns matching build output files) would also make sense
493for other users who clone your repository.</p><p>If you wish the exclude patterns to affect only certain repositories
494(instead of every repository for a given project), you may instead put
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]495them in a file in your repository named <code class="literal">.git/info/exclude</code>, or in any
496file specified by the <code class="literal">core.excludesfile</code> configuration variable.
497Some Git commands can also take exclude patterns directly on the
498command line. See <a class="ulink" href="gitignore.html" target="_top">gitignore(5)</a> for the details.</p></div><div class="section" title="How to merge"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-merge"></a>How to merge</h2></div></div></div><p>You can rejoin two diverging branches of development using
499<a class="ulink" href="git-merge.html" target="_top">git-merge(1)</a>:</p><pre class="literallayout">$ git merge branchname</pre><p>merges the development in the branch <code class="literal">branchname</code> into the current
500branch.</p><p>A merge is made by combining the changes made in <code class="literal">branchname</code> and the
Junio C Hamano5706e0b2009-11-24 10:54:16[diff] [blame]501changes made up to the latest commit in your current branch since
502their histories forked. The work tree is overwritten by the result of
503the merge when this combining is done cleanly, or overwritten by a
504half-merged results when this combining results in conflicts.
505Therefore, if you have uncommitted changes touching the same files as
506the ones impacted by the merge, Git will refuse to proceed. Most of
507the time, you will want to commit your changes before you can merge,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]508and if you don’t, then <a class="ulink" href="git-stash.html" target="_top">git-stash(1)</a> can take these changes
509away while you’re doing the merge, and reapply them afterwards.</p><p>If the changes are independent enough, Git will automatically complete
Junio C Hamano5706e0b2009-11-24 10:54:16[diff] [blame]510the merge and commit the result (or reuse an existing commit in case
511of <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>, see below). On the other hand,
512if there are conflicts—for example, if the same file is
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]513modified in two different ways in the remote branch and the local
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]514branch—then you are warned; the output may look something like this:</p><pre class="literallayout">$ git merge next
515 100% (4/4) done
516Auto-merged file.txt
517CONFLICT (content): Merge conflict in file.txt
518Automatic merge failed; fix conflicts and then commit the result.</pre><p>Conflict markers are left in the problematic files, and after
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]519you resolve the conflicts manually, you can update the index
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]520with the contents and run Git commit, as you normally would when
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]521creating a new file.</p><p>If you examine the resulting commit using gitk, you will see that it
522has two parents, one pointing to the top of the current branch, and
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]523one to the top of the other branch.</p></div><div class="section" title="Resolving a merge"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="resolving-a-merge"></a>Resolving a merge</h2></div></div></div><p>When a merge isn’t resolved automatically, Git leaves the index and
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]524the working tree in a special state that gives you all the
525information you need to help resolve the merge.</p><p>Files with conflicts are marked specially in the index, so until you
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]526resolve the problem and update the index, <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a> will
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]527fail:</p><pre class="literallayout">$ git commit
528file.txt: needs merge</pre><p>Also, <a class="ulink" href="git-status.html" target="_top">git-status(1)</a> will list those files as "unmerged", and the
529files with conflicts will have conflict markers added, like this:</p><pre class="literallayout">&lt;&lt;&lt;&lt;&lt;&lt;&lt; HEAD:file.txt
530Hello world
531=======
532Goodbye
533&gt;&gt;&gt;&gt;&gt;&gt;&gt; 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</pre><p>All you need to do is edit the files to resolve the conflicts, and then</p><pre class="literallayout">$ git add file.txt
534$ git commit</pre><p>Note that the commit message will already be filled in for you with
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]535some information about the merge. Normally you can just use this
536default message unchanged, but you may add additional commentary of
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]537your own if desired.</p><p>The above is all you need to know to resolve a simple merge. But Git
538also provides more information to help resolve conflicts:</p><div class="section" title="Getting conflict-resolution help during a merge"><div class="titlepage"><div><div><h3 class="title"><a name="conflict-resolution"></a>Getting conflict-resolution help during a merge</h3></div></div></div><p>All of the changes that Git was able to merge automatically are
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]539already added to the index file, so <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a> shows only
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]540the conflicts. It uses an unusual syntax:</p><pre class="literallayout">$ git diff
541diff --cc file.txt
542index 802992c,2b60207..0000000
543--- a/file.txt
544+++ b/file.txt
545@@@ -1,1 -1,1 +1,5 @@@
546++&lt;&lt;&lt;&lt;&lt;&lt;&lt; HEAD:file.txt
547 +Hello world
548++=======
549+ Goodbye
550++&gt;&gt;&gt;&gt;&gt;&gt;&gt; 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</pre><p>Recall that the commit which will be committed after we resolve this
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]551conflict will have two parents instead of the usual one: one parent
552will be HEAD, the tip of the current branch; the other will be the
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]553tip of the other branch, which is stored temporarily in MERGE_HEAD.</p><p>During the merge, the index holds three versions of each file. Each of
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]554these three "file stages" represents a different version of the file:</p><pre class="literallayout">$ git show :1:file.txt # the file in a common ancestor of both branches
555$ git show :2:file.txt # the version from HEAD.
556$ git show :3:file.txt # the version from MERGE_HEAD.</pre><p>When you ask <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a> to show the conflicts, it runs a
Junio C Hamano6fb124c2008-06-13 10:04:01[diff] [blame]557three-way diff between the conflicted merge results in the work tree with
558stages 2 and 3 to show only hunks whose contents come from both sides,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]559mixed (in other words, when a hunk’s merge results come only from stage 2,
Junio C Hamano6fb124c2008-06-13 10:04:01[diff] [blame]560that part is not conflicting and is not shown. Same for stage 3).</p><p>The diff above shows the differences between the working-tree version of
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]561file.txt and the stage 2 and stage 3 versions. So instead of preceding
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]562each line by a single <code class="literal">+</code> or <code class="literal">-</code>, it now uses two columns: the first
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]563column is used for differences between the first parent and the working
564directory copy, and the second for differences between the second parent
565and the working directory copy. (See the "COMBINED DIFF FORMAT" section
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]566of <a class="ulink" href="git-diff-files.html" target="_top">git-diff-files(1)</a> for a details of the format.)</p><p>After resolving the conflict in the obvious way (but before updating the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]567index), the diff will look like:</p><pre class="literallayout">$ git diff
568diff --cc file.txt
569index 802992c,2b60207..0000000
570--- a/file.txt
571+++ b/file.txt
572@@@ -1,1 -1,1 +1,1 @@@
573- Hello world
574 -Goodbye
575++Goodbye world</pre><p>This shows that our resolved version deleted "Hello world" from the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]576first parent, deleted "Goodbye" from the second parent, and added
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]577"Goodbye world", which was previously absent from both.</p><p>Some special diff options allow diffing the working directory against
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]578any of these stages:</p><pre class="literallayout">$ git diff -1 file.txt # diff against stage 1
579$ git diff --base file.txt # same as the above
580$ git diff -2 file.txt # diff against stage 2
581$ git diff --ours file.txt # same as the above
582$ git diff -3 file.txt # diff against stage 3
583$ git diff --theirs file.txt # same as the above.</pre><p>The <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> and <a class="ulink" href="gitk.html" target="_top">gitk(1)</a> commands also provide special help
584for merges:</p><pre class="literallayout">$ git log --merge
585$ gitk --merge</pre><p>These will display all commits which exist only on HEAD or on
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]586MERGE_HEAD, and which touch an unmerged file.</p><p>You may also use <a class="ulink" href="git-mergetool.html" target="_top">git-mergetool(1)</a>, which lets you merge the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]587unmerged files using external tools such as Emacs or kdiff3.</p><p>Each time you resolve the conflicts in a file and update the index:</p><pre class="literallayout">$ git add file.txt</pre><p>the different stages of that file will be "collapsed", after which
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]588<code class="literal">git diff</code> will (by default) no longer show diffs for that file.</p></div></div><div class="section" title="Undoing a merge"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="undoing-a-merge"></a>Undoing a merge</h2></div></div></div><p>If you get stuck and decide to just give up and throw the whole mess
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]589away, you can always return to the pre-merge state with</p><pre class="literallayout">$ git reset --hard HEAD</pre><p>Or, if you’ve already committed the merge that you want to throw away,</p><pre class="literallayout">$ git reset --hard ORIG_HEAD</pre><p>However, this last command can be dangerous in some cases—never
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]590throw away a commit you have already committed if that commit may
591itself have been merged into another branch, as doing so may confuse
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]592further merges.</p></div><div class="section" title="Fast-forward merges"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fast-forwards"></a>Fast-forward merges</h2></div></div></div><p>There is one special case not mentioned above, which is treated
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]593differently. Normally, a merge results in a merge commit, with two
594parents, one pointing at each of the two lines of development that
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]595were merged.</p><p>However, if the current branch is a descendant of the other—so every
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]596commit present in the one is already contained in the other—then Git
Junio C Hamano3f680f32009-11-16 02:10:54[diff] [blame]597just performs a "fast-forward"; the head of the current branch is moved
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]598forward to point at the head of the merged-in branch, without any new
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]599commits being created.</p></div><div class="section" title="Fixing mistakes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fixing-mistakes"></a>Fixing mistakes</h2></div></div></div><p>If you’ve messed up the working tree, but haven’t yet committed your
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]600mistake, you can return the entire working tree to the last committed
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]601state with</p><pre class="literallayout">$ git reset --hard HEAD</pre><p>If you make a commit that you later wish you hadn’t, there are two
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]602fundamentally different ways to fix the problem:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]603You can create a new commit that undoes whatever was done
Junio C Hamano8c5802d2007-11-15 00:13:36[diff] [blame]604 by the old commit. This is the correct thing if your
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]605 mistake has already been made public.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]606</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]607You can go back and modify the old commit. You should
608 never do this if you have already made the history public;
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]609 Git does not normally expect the "history" of a project to
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]610 change, and cannot correctly perform repeated merges from
611 a branch that has had its history changed.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]612</li></ol></div><div class="section" title="Fixing a mistake with a new commit"><div class="titlepage"><div><div><h3 class="title"><a name="reverting-a-commit"></a>Fixing a mistake with a new commit</h3></div></div></div><p>Creating a new commit that reverts an earlier change is very easy;
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]613just pass the <a class="ulink" href="git-revert.html" target="_top">git-revert(1)</a> command a reference to the bad
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]614commit; for example, to revert the most recent commit:</p><pre class="literallayout">$ git revert HEAD</pre><p>This will create a new commit which undoes the change in HEAD. You
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]615will be given a chance to edit the commit message for the new commit.</p><p>You can also revert an earlier change, for example, the next-to-last:</p><pre class="literallayout">$ git revert HEAD^</pre><p>In this case Git will attempt to undo the old change while leaving
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]616intact any changes made since then. If more recent changes overlap
617with the changes to be reverted, then you will be asked to fix
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]618conflicts manually, just as in the case of <a class="link" href="#resolving-a-merge" title="Resolving a merge">resolving a merge</a>.</p></div><div class="section" title="Fixing a mistake by rewriting history"><div class="titlepage"><div><div><h3 class="title"><a name="fixing-a-mistake-by-rewriting-history"></a>Fixing a mistake by rewriting history</h3></div></div></div><p>If the problematic commit is the most recent commit, and you have not
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]619yet made that commit public, then you may just
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]620<a class="link" href="#undoing-a-merge" title="Undoing a merge">destroy it using <code class="literal">git reset</code></a>.</p><p>Alternatively, you
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]621can edit the working directory and update the index to fix your
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]622mistake, just as if you were going to <a class="link" href="#how-to-make-a-commit" title="How to make a commit">create a new commit</a>, then run</p><pre class="literallayout">$ git commit --amend</pre><p>which will replace the old commit by a new commit incorporating your
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]623changes, giving you a chance to edit the old commit message first.</p><p>Again, you should never do this to a commit that may already have
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]624been merged into another branch; use <a class="ulink" href="git-revert.html" target="_top">git-revert(1)</a> instead in
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]625that case.</p><p>It is also possible to replace commits further back in the history, but
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]626this is an advanced topic to be left for
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]627<a class="link" href="#cleaning-up-history" title="Chapter 5. Rewriting history and maintaining patch series">another chapter</a>.</p></div><div class="section" title="Checking out an old version of a file"><div class="titlepage"><div><div><h3 class="title"><a name="checkout-of-path"></a>Checking out an old version of a file</h3></div></div></div><p>In the process of undoing a previous bad change, you may find it
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]628useful to check out an older version of a particular file using
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]629<a class="ulink" href="git-checkout.html" target="_top">git-checkout(1)</a>. We’ve used <code class="literal">git checkout</code> before to switch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]630branches, but it has quite different behavior if it is given a path
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]631name: the command</p><pre class="literallayout">$ git checkout HEAD^ path/to/file</pre><p>replaces path/to/file by the contents it had in the commit HEAD^, and
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]632also updates the index to match. It does not change branches.</p><p>If you just want to look at an old version of the file, without
633modifying the working directory, you can do that with
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]634<a class="ulink" href="git-show.html" target="_top">git-show(1)</a>:</p><pre class="literallayout">$ git show HEAD^:path/to/file</pre><p>which will display the given version of the file.</p></div><div class="section" title="Temporarily setting aside work in progress"><div class="titlepage"><div><div><h3 class="title"><a name="interrupted-work"></a>Temporarily setting aside work in progress</h3></div></div></div><p>While you are in the middle of working on something complicated, you
Junio C Hamano4cd1c0e2007-08-06 04:39:14[diff] [blame]635find an unrelated but obvious and trivial bug. You would like to fix it
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]636before continuing. You can use <a class="ulink" href="git-stash.html" target="_top">git-stash(1)</a> to save the current
Junio C Hamano4cd1c0e2007-08-06 04:39:14[diff] [blame]637state of your work, and after fixing the bug (or, optionally after doing
638so on a different branch and then coming back), unstash the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]639work-in-progress changes.</p><pre class="literallayout">$ git stash save "work in progress for foo feature"</pre><p>This command will save your changes away to the <code class="literal">stash</code>, and
Junio C Hamano4cd1c0e2007-08-06 04:39:14[diff] [blame]640reset your working tree and the index to match the tip of your
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]641current branch. Then you can make your fix as usual.</p><pre class="literallayout">... edit and test ...
642$ git commit -a -m "blorpl: typofix"</pre><p>After that, you can go back to what you were working on with
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]643<code class="literal">git stash pop</code>:</p><pre class="literallayout">$ git stash pop</pre></div></div><div class="section" title="Ensuring good performance"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ensuring-good-performance"></a>Ensuring good performance</h2></div></div></div><p>On large repositories, Git depends on compression to keep the history
Junio C Hamano8c5696d2013-02-11 05:35:00[diff] [blame]644information from taking up too much space on disk or in memory. Some
645Git commands may automatically run <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a>, so you don’t
646have to worry about running it manually. However, compressing a large
647repository may take a while, so you may want to call <code class="literal">gc</code> explicitly
648to avoid automatic compression kicking in when it is not convenient.</p></div><div class="section" title="Ensuring reliability"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ensuring-reliability"></a>Ensuring reliability</h2></div></div></div><div class="section" title="Checking the repository for corruption"><div class="titlepage"><div><div><h3 class="title"><a name="checking-for-corruption"></a>Checking the repository for corruption</h3></div></div></div><p>The <a class="ulink" href="git-fsck.html" target="_top">git-fsck(1)</a> command runs a number of self-consistency checks
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]649on the repository, and reports on any problems. This may take some
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]650time.</p><pre class="literallayout">$ git fsck
651dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
652dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
653dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
654dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
655dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
656dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
657dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
658dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
659...</pre><p>You will see informational messages on dangling objects. They are objects
Junio C Hamano81d540a2012-03-02 19:52:47[diff] [blame]660that still exist in the repository but are no longer referenced by any of
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]661your branches, and can (and will) be removed after a while with <code class="literal">gc</code>.
Junio C Hamano010705a2012-06-19 23:37:26[diff] [blame]662You can run <code class="literal">git fsck --no-dangling</code> to suppress these messages, and still
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]663view real errors.</p></div><div class="section" title="Recovering lost changes"><div class="titlepage"><div><div><h3 class="title"><a name="recovering-lost-changes"></a>Recovering lost changes</h3></div></div></div><div class="section" title="Reflogs"><div class="titlepage"><div><div><h4 class="title"><a name="reflogs"></a>Reflogs</h4></div></div></div><p>Say you modify a branch with <a class="link" href="#fixing-mistakes" title="Fixing mistakes"><code class="literal">git reset --hard</code></a>,
664and then realize that the branch was the only reference you had to
665that point in history.</p><p>Fortunately, Git also keeps a log, called a "reflog", of all the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]666previous values of each branch. So in this case you can still find the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]667old history using, for example,</p><pre class="literallayout">$ git log master@{1}</pre><p>This lists the commits reachable from the previous version of the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]668<code class="literal">master</code> branch head. This syntax can be used with any Git command
669that accepts a commit, not just with <code class="literal">git log</code>. Some other examples:</p><pre class="literallayout">$ git show master@{2} # See where the branch pointed 2,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]670$ git show master@{3} # 3, ... changes ago.
671$ gitk master@{yesterday} # See where it pointed yesterday,
672$ gitk master@{"1 week ago"} # ... or last week
673$ git log --walk-reflogs master # show reflog entries for master</pre><p>A separate reflog is kept for the HEAD, so</p><pre class="literallayout">$ git show HEAD@{"1 week ago"}</pre><p>will show what HEAD pointed to one week ago, not what the current branch
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]674pointed to one week ago. This allows you to see the history of what
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]675you’ve checked out.</p><p>The reflogs are kept by default for 30 days, after which they may be
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]676pruned. See <a class="ulink" href="git-reflog.html" target="_top">git-reflog(1)</a> and <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a> to learn
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]677how to control this pruning, and see the "SPECIFYING REVISIONS"
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]678section of <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a> for details.</p><p>Note that the reflog history is very different from normal Git history.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]679While normal history is shared by every repository that works on the
680same project, the reflog history is not shared: it tells you only about
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]681how the branches in your local repository have changed over time.</p></div><div class="section" title="Examining dangling objects"><div class="titlepage"><div><div><h4 class="title"><a name="dangling-object-recovery"></a>Examining dangling objects</h4></div></div></div><p>In some situations the reflog may not be able to save you. For example,
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]682suppose you delete a branch, then realize you need the history it
683contained. The reflog is also deleted; however, if you have not yet
684pruned the repository, then you may still be able to find the lost
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]685commits in the dangling objects that <code class="literal">git fsck</code> reports. See
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]686<a class="xref" href="#dangling-objects" title="Dangling objects">the section called “Dangling objects”</a> for the details.</p><pre class="literallayout">$ git fsck
687dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
688dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
689dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
690...</pre><p>You can examine
691one of those dangling commits with, for example,</p><pre class="literallayout">$ gitk 7281251ddd --not --all</pre><p>which does what it sounds like: it says that you want to see the commit
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]692history that is described by the dangling commit(s), but not the
693history that is described by all your existing branches and tags. Thus
694you get exactly the history reachable from that commit that is lost.
695(And notice that it might not be just one commit: we only report the
696"tip of the line" as being dangling, but there might be a whole deep
Junio C Hamanodb911ee2007-02-28 08:13:52[diff] [blame]697and complex commit history that was dropped.)</p><p>If you decide you want the history back, you can always create a new
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]698reference pointing to it, for example, a new branch:</p><pre class="literallayout">$ git branch recovered-branch 7281251ddd</pre><p>Other types of dangling objects (blobs and trees) are also possible, and
Junio C Hamano8c5696d2013-02-11 05:35:00[diff] [blame]699dangling objects can arise in other situations.</p></div></div></div></div><div class="chapter" title="Chapter 4. Sharing development with others"><div class="titlepage"><div><div><h2 class="title"><a name="sharing-development"></a>Chapter 4. Sharing development with others</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#getting-updates-With-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#submitting-patches">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#importing-patches">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#public-repositories">Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="section"><a href="#sharing-development-examples">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></div><div class="section" title="Getting updates with git pull"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="getting-updates-With-git-pull"></a>Getting updates with git pull</h2></div></div></div><p>After you clone a repository and commit a few changes of your own, you
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]700may wish to check the original repository for updates and merge them
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]701into your own work.</p><p>We have already seen <a class="link" href="#Updating-a-repository-With-git-fetch" title="Updating a repository with git fetch">how to keep remote-tracking branches up to date</a> with <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]702and how to merge two branches. So you can merge in changes from the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]703original repository’s master branch with:</p><pre class="literallayout">$ git fetch
704$ git merge origin/master</pre><p>However, the <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a> command provides a way to do this in
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]705one step:</p><pre class="literallayout">$ git pull origin master</pre><p>In fact, if you have <code class="literal">master</code> checked out, then this branch has been
706configured by <code class="literal">git clone</code> to get changes from the HEAD branch of the
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]707origin repository. So often you can
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]708accomplish the above with just a simple</p><pre class="literallayout">$ git pull</pre><p>This command will fetch changes from the remote branches to your
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]709remote-tracking branches <code class="literal">origin/*</code>, and merge the default branch into
710the current branch.</p><p>More generally, a branch that is created from a remote-tracking branch
711will pull
Junio C Hamano4cd1c0e2007-08-06 04:39:14[diff] [blame]712by default from that branch. See the descriptions of the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]713<code class="literal">branch.&lt;name&gt;.remote</code> and <code class="literal">branch.&lt;name&gt;.merge</code> options in
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]714<a class="ulink" href="git-config.html" target="_top">git-config(1)</a>, and the discussion of the <code class="literal">--track</code> option in
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]715<a class="ulink" href="git-checkout.html" target="_top">git-checkout(1)</a>, to learn how to control these defaults.</p><p>In addition to saving you keystrokes, <code class="literal">git pull</code> also helps you by
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]716producing a default commit message documenting the branch and
717repository that you pulled from.</p><p>(But note that no such commit will be created in the case of a
Junio C Hamano3f680f32009-11-16 02:10:54[diff] [blame]718<a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>; instead, your branch will just be
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]719updated to point to the latest commit from the upstream branch.)</p><p>The <code class="literal">git pull</code> command can also be given <code class="literal">.</code> as the "remote" repository,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]720in which case it just merges in a branch from the current repository; so
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]721the commands</p><pre class="literallayout">$ git pull . branch
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]722$ git merge branch</pre><p>are roughly equivalent.</p></div><div class="section" title="Submitting patches to a project"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="submitting-patches"></a>Submitting patches to a project</h2></div></div></div><p>If you just have a few changes, the simplest way to submit them may
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]723just be to send them as patches in email:</p><p>First, use <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a>; for example:</p><pre class="literallayout">$ git format-patch origin</pre><p>will produce a numbered series of files in the current directory, one
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]724for each patch in the current branch but not in <code class="literal">origin/HEAD</code>.</p><p><code class="literal">git format-patch</code> can include an initial "cover letter". You can insert
Junio C Hamano4eb2b9c2012-11-15 21:12:29[diff] [blame]725commentary on individual patches after the three dash line which
726<code class="literal">format-patch</code> places after the commit message but before the patch
727itself. If you use <code class="literal">git notes</code> to track your cover letter material,
728<code class="literal">git format-patch --notes</code> will include the commit’s notes in a similar
729manner.</p><p>You can then import these into your mail client and send them by
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]730hand. However, if you have a lot to send at once, you may prefer to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]731use the <a class="ulink" href="git-send-email.html" target="_top">git-send-email(1)</a> script to automate the process.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]732Consult the mailing list for your project first to determine how they
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]733prefer such patches be handled.</p></div><div class="section" title="Importing patches to a project"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="importing-patches"></a>Importing patches to a project</h2></div></div></div><p>Git also provides a tool called <a class="ulink" href="git-am.html" target="_top">git-am(1)</a> (am stands for
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]734"apply mailbox"), for importing such an emailed series of patches.
735Just save all of the patch-containing messages, in order, into a
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]736single mailbox file, say <code class="literal">patches.mbox</code>, then run</p><pre class="literallayout">$ git am -3 patches.mbox</pre><p>Git will apply each patch in order; if any conflicts are found, it
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]737will stop, and you can fix the conflicts as described in
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]738"<a class="link" href="#resolving-a-merge" title="Resolving a merge">Resolving a merge</a>". (The <code class="literal">-3</code> option tells
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]739Git to perform a merge; if you would prefer it just to abort and
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]740leave your tree and index untouched, you may omit that option.)</p><p>Once the index is updated with the results of the conflict
Junio C Hamanoa1952302013-07-01 21:31:18[diff] [blame]741resolution, instead of creating a new commit, just run</p><pre class="literallayout">$ git am --continue</pre><p>and Git will create the commit for you and continue applying the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]742remaining patches from the mailbox.</p><p>The final result will be a series of commits, one for each patch in
743the original mailbox, with authorship and commit log message each
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]744taken from the message containing each patch.</p></div><div class="section" title="Public Git repositories"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="public-repositories"></a>Public Git repositories</h2></div></div></div><p>Another way to submit changes to a project is to tell the maintainer
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]745of that project to pull the changes from your repository using
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]746<a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>. In the section "<a class="link" href="#getting-updates-With-git-pull" title="Getting updates with git pull">Getting updates with <code class="literal">git pull</code></a>" we described this as a way to get
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]747updates from the "main" repository, but it works just as well in the
748other direction.</p><p>If you and the maintainer both have accounts on the same machine, then
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]749you can just pull changes from each other’s repositories directly;
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]750commands that accept repository URLs as arguments will also accept a
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]751local directory name:</p><pre class="literallayout">$ git clone /path/to/repository
752$ git pull /path/to/other/repository</pre><p>or an ssh URL:</p><pre class="literallayout">$ git clone ssh://yourhost/~you/repository</pre><p>For projects with few developers, or for synchronizing a few private
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]753repositories, this may be all you need.</p><p>However, the more common way to do this is to maintain a separate public
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]754repository (usually on a different host) for others to pull changes
755from. This is usually more convenient, and allows you to cleanly
756separate private work in progress from publicly visible work.</p><p>You will continue to do your day-to-day work in your personal
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]757repository, but periodically "push" changes from your personal
758repository into your public repository, allowing other developers to
759pull from that repository. So the flow of changes, in a situation
760where there is one other developer with a public repository, looks
761like this:</p><pre class="literallayout"> you push
762your personal repo ------------------&gt; your public repo
763 ^ |
764 | |
765 | you pull | they pull
766 | |
767 | |
768 | they push V
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]769their public repo &lt;------------------- their repo</pre><p>We explain how to do this in the following sections.</p><div class="section" title="Setting up a public repository"><div class="titlepage"><div><div><h3 class="title"><a name="setting-up-a-public-repository"></a>Setting up a public repository</h3></div></div></div><p>Assume your personal repository is in the directory <code class="literal">~/proj</code>. We
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]770first create a new clone of the repository and tell <code class="literal">git daemon</code> that it
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]771is meant to be public:</p><pre class="literallayout">$ git clone --bare ~/proj proj.git
772$ touch proj.git/git-daemon-export-ok</pre><p>The resulting directory proj.git contains a "bare" git repository—it is
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]773just the contents of the <code class="literal">.git</code> directory, without any files checked out
774around it.</p><p>Next, copy <code class="literal">proj.git</code> to the server where you plan to host the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]775public repository. You can use scp, rsync, or whatever is most
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]776convenient.</p></div><div class="section" title="Exporting a Git repository via the Git protocol"><div class="titlepage"><div><div><h3 class="title"><a name="exporting-via-git"></a>Exporting a Git repository via the Git protocol</h3></div></div></div><p>This is the preferred method.</p><p>If someone else administers the server, they should tell you what
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]777directory to put the repository in, and what <code class="literal">git://</code> URL it will
778appear at. You can then skip to the section
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]779"<a class="link" href="#pushing-changes-to-a-public-repository" title="Pushing changes to a public repository">Pushing changes to a public repository</a>", below.</p><p>Otherwise, all you need to do is start <a class="ulink" href="git-daemon.html" target="_top">git-daemon(1)</a>; it will
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]780listen on port 9418. By default, it will allow access to any directory
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]781that looks like a Git directory and contains the magic file
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]782git-daemon-export-ok. Passing some directory paths as <code class="literal">git daemon</code>
783arguments will further restrict the exports to those paths.</p><p>You can also run <code class="literal">git daemon</code> as an inetd service; see the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]784<a class="ulink" href="git-daemon.html" target="_top">git-daemon(1)</a> man page for details. (See especially the
Junio C Hamano8c5696d2013-02-11 05:35:00[diff] [blame]785examples section.)</p></div><div class="section" title="Exporting a git repository via HTTP"><div class="titlepage"><div><div><h3 class="title"><a name="exporting-via-http"></a>Exporting a git repository via HTTP</h3></div></div></div><p>The Git protocol gives better performance and reliability, but on a
786host with a web server set up, HTTP exports may be simpler to set up.</p><p>All you need to do is place the newly created bare Git repository in
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]787a directory that is exported by the web server, and make some
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]788adjustments to give web clients some extra information they need:</p><pre class="literallayout">$ mv proj.git /home/you/public_html/proj.git
789$ cd proj.git
790$ git --bare update-server-info
791$ mv hooks/post-update.sample hooks/post-update</pre><p>(For an explanation of the last two lines, see
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]792<a class="ulink" href="git-update-server-info.html" target="_top">git-update-server-info(1)</a> and <a class="ulink" href="githooks.html" target="_top">githooks(5)</a>.)</p><p>Advertise the URL of <code class="literal">proj.git</code>. Anybody else should then be able to
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]793clone or pull from that URL, for example with a command line like:</p><pre class="literallayout">$ git clone http://yourserver.com/~you/proj.git</pre><p>(See also
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]794<a class="ulink" href="howto/setup-git-server-over-http.html" target="_top">setup-git-server-over-http</a>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]795for a slightly more sophisticated setup using WebDAV which also
Junio C Hamano8c5696d2013-02-11 05:35:00[diff] [blame]796allows pushing over HTTP.)</p></div><div class="section" title="Pushing changes to a public repository"><div class="titlepage"><div><div><h3 class="title"><a name="pushing-changes-to-a-public-repository"></a>Pushing changes to a public repository</h3></div></div></div><p>Note that the two techniques outlined above (exporting via
797<a class="link" href="#exporting-via-http" title="Exporting a git repository via HTTP">http</a> or <a class="link" href="#exporting-via-git" title="Exporting a Git repository via the Git protocol">git</a>) allow other
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]798maintainers to fetch your latest changes, but they do not allow write
799access, which you will need to update the public repository with the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]800latest changes created in your private repository.</p><p>The simplest way to do this is using <a class="ulink" href="git-push.html" target="_top">git-push(1)</a> and ssh; to
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]801update the remote branch named <code class="literal">master</code> with the latest state of your
802branch named <code class="literal">master</code>, run</p><pre class="literallayout">$ git push ssh://yourserver.com/~you/proj.git master:master</pre><p>or just</p><pre class="literallayout">$ git push ssh://yourserver.com/~you/proj.git master</pre><p>As with <code class="literal">git fetch</code>, <code class="literal">git push</code> will complain if this does not result in a
Junio C Hamano3f680f32009-11-16 02:10:54[diff] [blame]803<a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>; see the following section for details on
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]804handling this case.</p><p>Note that the target of a <code class="literal">push</code> is normally a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]805<a class="link" href="#def_bare_repository">bare</a> repository. You can also push to a
Junio C Hamano0292db32013-02-15 23:23:28[diff] [blame]806repository that has a checked-out working tree, but a push to update the
807currently checked-out branch is denied by default to prevent confusion.
Junio C Hamano5dab5a92013-02-25 18:51:24[diff] [blame]808See the description of the receive.denyCurrentBranch option
Junio C Hamano0292db32013-02-15 23:23:28[diff] [blame]809in <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.</p><p>As with <code class="literal">git fetch</code>, you may also set up configuration options to
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]810save typing; so, for example:</p><pre class="literallayout">$ git remote add public-repo ssh://yourserver.com/~you/proj.git</pre><p>adds the following to <code class="literal">.git/config</code>:</p><pre class="literallayout">[remote "public-repo"]
811 url = yourserver.com:proj.git
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]812 fetch = +refs/heads/*:refs/remotes/example/*</pre><p>which lets you do the same push with just</p><pre class="literallayout">$ git push public-repo master</pre><p>See the explanations of the <code class="literal">remote.&lt;name&gt;.url</code>,
813<code class="literal">branch.&lt;name&gt;.remote</code>, and <code class="literal">remote.&lt;name&gt;.push</code> options in
814<a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.</p></div><div class="section" title="What to do when a push fails"><div class="titlepage"><div><div><h3 class="title"><a name="forcing-push"></a>What to do when a push fails</h3></div></div></div><p>If a push would not result in a <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a> of the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]815remote branch, then it will fail with an error like:</p><pre class="literallayout">error: remote 'refs/heads/master' is not an ancestor of
816 local 'refs/heads/master'.
817 Maybe you are not up-to-date and need to pull first?
818error: failed to push to 'ssh://yourserver.com/~you/proj.git'</pre><p>This can happen, for example, if you:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]819use <code class="literal">git reset --hard</code> to remove already-published commits, or
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]820</li><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]821use <code class="literal">git commit --amend</code> to replace already-published commits
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]822 (as in <a class="xref" href="#fixing-a-mistake-by-rewriting-history" title="Fixing a mistake by rewriting history">the section called “Fixing a mistake by rewriting history”</a>), or
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]823</li><li class="listitem">
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]824use <code class="literal">git rebase</code> to rebase any already-published commits (as
825 in <a class="xref" href="#using-git-rebase" title="Keeping a patch series up to date using git rebase">the section called “Keeping a patch series up to date using git rebase”</a>).
826</li></ul></div><p>You may force <code class="literal">git push</code> to perform the update anyway by preceding the
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]827branch name with a plus sign:</p><pre class="literallayout">$ git push ssh://yourserver.com/~you/proj.git +master</pre><p>Note the addition of the <code class="literal">+</code> sign. Alternatively, you can use the
828<code class="literal">-f</code> flag to force the remote update, as in:</p><pre class="literallayout">$ git push -f ssh://yourserver.com/~you/proj.git master</pre><p>Normally whenever a branch head in a public repository is modified, it
Junio C Hamano878cc1e2007-12-14 08:35:13[diff] [blame]829is modified to point to a descendant of the commit that it pointed to
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]830before. By forcing a push in this situation, you break that convention.
Junio C Hamanoec87f522008-12-10 08:35:25[diff] [blame]831(See <a class="xref" href="#problems-With-rewriting-history" title="Problems with rewriting history">the section called “Problems with rewriting history”</a>.)</p><p>Nevertheless, this is a common practice for people that need a simple
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]832way to publish a work-in-progress patch series, and it is an acceptable
833compromise as long as you warn other developers that this is how you
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]834intend to manage the branch.</p><p>It’s also possible for a push to fail in this way when other people have
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]835the right to push to the same repository. In that case, the correct
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]836solution is to retry the push after first updating your work: either by a
837pull, or by a fetch followed by a rebase; see the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]838<a class="link" href="#setting-up-a-shared-repository" title="Setting up a shared repository">next section</a> and
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]839<a class="ulink" href="gitcvs-migration.html" target="_top">gitcvs-migration(7)</a> for more.</p></div><div class="section" title="Setting up a shared repository"><div class="titlepage"><div><div><h3 class="title"><a name="setting-up-a-shared-repository"></a>Setting up a shared repository</h3></div></div></div><p>Another way to collaborate is by using a model similar to that
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]840commonly used in CVS, where several developers with special rights
841all push to and pull from a single shared repository. See
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]842<a class="ulink" href="gitcvs-migration.html" target="_top">gitcvs-migration(7)</a> for instructions on how to
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]843set this up.</p><p>However, while there is nothing wrong with Git’s support for shared
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]844repositories, this mode of operation is not generally recommended,
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]845simply because the mode of collaboration that Git supports—by
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]846exchanging patches and pulling from public repositories—has so many
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]847advantages over the central shared repository:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]848Git’s ability to quickly import and merge patches allows a
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]849 single maintainer to process incoming changes even at very
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]850 high rates. And when that becomes too much, <code class="literal">git pull</code> provides
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]851 an easy way for that maintainer to delegate this job to other
852 maintainers while still allowing optional review of incoming
853 changes.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]854</li><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]855Since every developer’s repository has the same complete copy
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]856 of the project history, no repository is special, and it is
857 trivial for another developer to take over maintenance of a
858 project, either by mutual agreement, or because a maintainer
859 becomes unresponsive or difficult to work with.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]860</li><li class="listitem">
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]861The lack of a central group of "committers" means there is
862 less need for formal decisions about who is "in" and who is
863 "out".
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]864</li></ul></div></div><div class="section" title="Allowing web browsing of a repository"><div class="titlepage"><div><div><h3 class="title"><a name="setting-up-gitweb"></a>Allowing web browsing of a repository</h3></div></div></div><p>The gitweb cgi script provides users an easy way to browse your
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]865project’s files and history without having to install Git; see the file
866gitweb/INSTALL in the Git source tree for instructions on setting it up.</p></div></div><div class="section" title="Examples"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sharing-development-examples"></a>Examples</h2></div></div></div><div class="section" title="Maintaining topic branches for a Linux subsystem maintainer"><div class="titlepage"><div><div><h3 class="title"><a name="maintaining-topic-branches"></a>Maintaining topic branches for a Linux subsystem maintainer</h3></div></div></div><p>This describes how Tony Luck uses Git in his role as maintainer of the
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]867IA64 architecture for the Linux kernel.</p><p>He uses two public branches:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]868A "test" tree into which patches are initially placed so that they
869 can get some exposure when integrated with other ongoing development.
870 This tree is available to Andrew for pulling into -mm whenever he
871 wants.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]872</li><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]873A "release" tree into which tested patches are moved for final sanity
874 checking, and as a vehicle to send them upstream to Linus (by sending
875 him a "please pull" request.)
876</li></ul></div><p>He also uses a set of temporary branches ("topic branches"), each
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]877containing a logical grouping of patches.</p><p>To set this up, first create your work tree by cloning Linus’s public
Junio C Hamanoa1952302013-07-01 21:31:18[diff] [blame]878tree:</p><pre class="literallayout">$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]879$ cd work</pre><p>Linus’s tree will be stored in the remote-tracking branch named origin/master,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]880and can be updated using <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>; you can track other
881public trees using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a> to set up a "remote" and
882<a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> to keep them up-to-date; see
883<a class="xref" href="#repositories-and-branches" title="Chapter 1. Repositories and Branches">Chapter 1, <i>Repositories and Branches</i></a>.</p><p>Now create the branches in which you are going to work; these start out
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]884at the current tip of origin/master branch, and should be set up (using
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]885the <code class="literal">--track</code> option to <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a>) to merge changes in from
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]886Linus by default.</p><pre class="literallayout">$ git branch --track test origin/master
887$ git branch --track release origin/master</pre><p>These can be easily kept up to date using <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>.</p><pre class="literallayout">$ git checkout test &amp;&amp; git pull
888$ git checkout release &amp;&amp; git pull</pre><p>Important note! If you have any local changes in these branches, then
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]889this merge will create a commit object in the history (with no local
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]890changes Git will simply do a "fast-forward" merge). Many people dislike
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]891the "noise" that this creates in the Linux history, so you should avoid
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]892doing this capriciously in the <code class="literal">release</code> branch, as these noisy commits
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]893will become part of the permanent history when you ask Linus to pull
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]894from the release branch.</p><p>A few configuration variables (see <a class="ulink" href="git-config.html" target="_top">git-config(1)</a>) can
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]895make it easy to push both branches to your public tree. (See
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]896<a class="xref" href="#setting-up-a-public-repository" title="Setting up a public repository">the section called “Setting up a public repository”</a>.)</p><pre class="literallayout">$ cat &gt;&gt; .git/config &lt;&lt;EOF
897[remote "mytree"]
Junio C Hamanoa1952302013-07-01 21:31:18[diff] [blame]898 url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]899 push = release
900 push = test
901EOF</pre><p>Then you can push both the test and release trees using
902<a class="ulink" href="git-push.html" target="_top">git-push(1)</a>:</p><pre class="literallayout">$ git push mytree</pre><p>or push just one of the test and release branches using:</p><pre class="literallayout">$ git push mytree test</pre><p>or</p><pre class="literallayout">$ git push mytree release</pre><p>Now to apply some patches from the community. Think of a short
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]903snappy name for a branch to hold this patch (or related group of
Junio C Hamanoc27b7332010-10-14 04:37:28[diff] [blame]904patches), and create a new branch from a recent stable tag of
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]905Linus’s branch. Picking a stable base for your branch will:
Junio C Hamanoc27b7332010-10-14 04:37:28[diff] [blame]9061) help you: by avoiding inclusion of unrelated and perhaps lightly
907tested changes
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]9082) help future bug hunters that use <code class="literal">git bisect</code> to find problems</p><pre class="literallayout">$ git checkout -b speed-up-spinlocks v2.6.35</pre><p>Now you apply the patch(es), run some tests, and commit the change(s). If
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]909the patch is a multi-part series, then you should apply each as a separate
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]910commit to this branch.</p><pre class="literallayout">$ ... patch ... test ... commit [ ... patch ... test ... commit ]*</pre><p>When you are happy with the state of this change, you can merge it into the
911"test" branch in preparation to make it public:</p><pre class="literallayout">$ git checkout test &amp;&amp; git merge speed-up-spinlocks</pre><p>It is unlikely that you would have any conflicts here … but you might if you
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]912spent a while on this step and had also pulled new versions from upstream.</p><p>Some time later when enough time has passed and testing done, you can pull the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]913same branch into the <code class="literal">release</code> tree ready to go upstream. This is where you
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]914see the value of keeping each patch (or patch series) in its own branch. It
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]915means that the patches can be moved into the <code class="literal">release</code> tree in any order.</p><pre class="literallayout">$ git checkout release &amp;&amp; git merge speed-up-spinlocks</pre><p>After a while, you will have a number of branches, and despite the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]916well chosen names you picked for each of them, you may forget what
917they are for, or what status they are in. To get a reminder of what
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]918changes are in a specific branch, use:</p><pre class="literallayout">$ git log linux..branchname | git shortlog</pre><p>To see whether it has already been merged into the test or release branches,
919use:</p><pre class="literallayout">$ git log test..branchname</pre><p>or</p><pre class="literallayout">$ git log release..branchname</pre><p>(If this branch has not yet been merged, you will see some log entries.
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]920If it has been merged, then there will be no output.)</p><p>Once a patch completes the great cycle (moving from test to release,
921then pulled by Linus, and finally coming back into your local
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]922<code class="literal">origin/master</code> branch), the branch for this change is no longer needed.
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]923You detect this when the output from:</p><pre class="literallayout">$ git log origin..branchname</pre><p>is empty. At this point the branch can be deleted:</p><pre class="literallayout">$ git branch -d branchname</pre><p>Some changes are so trivial that it is not necessary to create a separate
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]924branch and then merge into each of the test and release branches. For
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]925these changes, just apply directly to the <code class="literal">release</code> branch, and then
926merge that into the <code class="literal">test</code> branch.</p><p>After pushing your work to <code class="literal">mytree</code>, you can use
Junio C Hamano5dab5a92013-02-25 18:51:24[diff] [blame]927<a class="ulink" href="git-request-pull.html" target="_top">git-request-pull(1)</a> to prepare a "please pull" request message
928to send to Linus:</p><pre class="literallayout">$ git push mytree
929$ git request-pull origin mytree release</pre><p>Here are some of the scripts that simplify all this even further.</p><pre class="literallayout">==== update script ====
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]930# Update a branch in my Git tree. If the branch to be updated
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]931# is origin, then pull from kernel.org. Otherwise merge
932# origin/master branch into test|release branch
933
934case "$1" in
935test|release)
936 git checkout $1 &amp;&amp; git pull . origin
937 ;;
938origin)
939 before=$(git rev-parse refs/remotes/origin/master)
940 git fetch origin
941 after=$(git rev-parse refs/remotes/origin/master)
942 if [ $before != $after ]
943 then
944 git log $before..$after | git shortlog
945 fi
946 ;;
947*)
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]948 echo "usage: $0 origin|test|release" 1&gt;&amp;2
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]949 exit 1
950 ;;
951esac</pre><pre class="literallayout">==== merge script ====
952# Merge a branch into either the test or release branch
953
954pname=$0
955
956usage()
957{
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]958 echo "usage: $pname branch test|release" 1&gt;&amp;2
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]959 exit 1
960}
961
962git show-ref -q --verify -- refs/heads/"$1" || {
963 echo "Can't see branch &lt;$1&gt;" 1&gt;&amp;2
964 usage
965}
966
967case "$2" in
968test|release)
969 if [ $(git log $2..$1 | wc -c) -eq 0 ]
970 then
971 echo $1 already merged into $2 1&gt;&amp;2
972 exit 1
973 fi
974 git checkout $2 &amp;&amp; git pull . $1
975 ;;
976*)
977 usage
978 ;;
979esac</pre><pre class="literallayout">==== status script ====
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]980# report on status of my ia64 Git tree
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]981
982gb=$(tput setab 2)
983rb=$(tput setab 1)
984restore=$(tput setab 9)
985
986if [ `git rev-list test..release | wc -c` -gt 0 ]
987then
988 echo $rb Warning: commits in release that are not in test $restore
989 git log test..release
990fi
991
992for branch in `git show-ref --heads | sed 's|^.*/||'`
993do
994 if [ $branch = test -o $branch = release ]
995 then
996 continue
997 fi
998
999 echo -n $gb ======= $branch ====== $restore " "
1000 status=
1001 for ref in test release origin/master
1002 do
1003 if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
1004 then
1005 status=$status${ref:0:1}
1006 fi
1007 done
1008 case $status in
1009 trl)
1010 echo $rb Need to pull into test $restore
1011 ;;
1012 rl)
1013 echo "In test"
1014 ;;
1015 l)
1016 echo "Waiting for linus"
1017 ;;
1018 "")
1019 echo $rb All done $restore
1020 ;;
1021 *)
1022 echo $rb "&lt;$status&gt;" $restore
1023 ;;
1024 esac
1025 git log origin/master..$branch | git shortlog
Junio C Hamano5dab5a92013-02-25 18:51:24[diff] [blame]1026done</pre></div></div></div><div class="chapter" title="Chapter 5. Rewriting history and maintaining patch series"><div class="titlepage"><div><div><h2 class="title"><a name="cleaning-up-history"></a>Chapter 5. Rewriting history and maintaining patch series</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#patch-series">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#using-git-rebase">Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="section"><a href="#rewriting-one-commit">Rewriting a single commit</a></span></dt><dt><span class="section"><a href="#reordering-patch-series">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#interactive-rebase">Using interactive rebases</a></span></dt><dt><span class="section"><a href="#patch-series-tools">Other tools</a></span></dt><dt><span class="section"><a href="#problems-With-rewriting-history">Problems with rewriting history</a></span></dt><dt><span class="section"><a href="#bisect-merges">Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></div><p>Normally commits are only added to a project, never taken away or
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1027replaced. Git is designed with this assumption, and violating it will
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1028cause Git’s merge machinery (for example) to do the wrong thing.</p><p>However, there is a situation in which it can be useful to violate this
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1029assumption.</p><div class="section" title="Creating the perfect patch series"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="patch-series"></a>Creating the perfect patch series</h2></div></div></div><p>Suppose you are a contributor to a large project, and you want to add a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1030complicated feature, and to present it to the other developers in a way
1031that makes it easy for them to read your changes, verify that they are
1032correct, and understand why you made each change.</p><p>If you present all of your changes as a single patch (or commit), they
Junio C Hamanodb911ee2007-02-28 08:13:52[diff] [blame]1033may find that it is too much to digest all at once.</p><p>If you present them with the entire history of your work, complete with
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1034mistakes, corrections, and dead ends, they may be overwhelmed.</p><p>So the ideal is usually to produce a series of patches such that:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1035Each patch can be applied in order.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1036</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1037Each patch includes a single logical change, together with a
1038 message explaining the change.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1039</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1040No patch introduces a regression: after applying any initial
1041 part of the series, the resulting project still compiles and
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1042 works, and has no bugs that it didn’t have before.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1043</li><li class="listitem">
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1044The complete series produces the same end result as your own
1045 (probably much messier!) development process did.
1046</li></ol></div><p>We will introduce some tools that can help you do this, explain how to
1047use them, and then explain some of the problems that can arise because
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1048you are rewriting history.</p></div><div class="section" title="Keeping a patch series up to date using git rebase"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="using-git-rebase"></a>Keeping a patch series up to date using git rebase</h2></div></div></div><p>Suppose that you create a branch <code class="literal">mywork</code> on a remote-tracking branch
1049<code class="literal">origin</code>, and create some commits on top of it:</p><pre class="literallayout">$ git checkout -b mywork origin
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1050$ vi file.txt
1051$ git commit
1052$ vi otherfile.txt
1053$ git commit
1054...</pre><p>You have performed no merges into mywork, so it is just a simple linear
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1055sequence of patches on top of <code class="literal">origin</code>:</p><pre class="literallayout"> o--o--O &lt;-- origin
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1056 \
Junio C Hamano3b4609d2010-09-30 00:04:34[diff] [blame]1057 a--b--c &lt;-- mywork</pre><p>Some more interesting work has been done in the upstream project, and
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1058<code class="literal">origin</code> has advanced:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1059 \
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1060 a--b--c &lt;-- mywork</pre><p>At this point, you could use <code class="literal">pull</code> to merge your changes back in;
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1061the result would create a new merge commit, like this:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1062 \ \
1063 a--b--c--m &lt;-- mywork</pre><p>However, if you prefer to keep the history in mywork a simple series of
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1064commits without any merges, you may instead choose to use
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1065<a class="ulink" href="git-rebase.html" target="_top">git-rebase(1)</a>:</p><pre class="literallayout">$ git checkout mywork
1066$ git rebase origin</pre><p>This will remove each of your commits from mywork, temporarily saving
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1067them as patches (in a directory named <code class="literal">.git/rebase-apply</code>), update mywork to
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1068point at the latest version of origin, then apply each of the saved
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1069patches to the new mywork. The result will look like:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1070 \
1071 a'--b'--c' &lt;-- mywork</pre><p>In the process, it may discover conflicts. In that case it will stop
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1072and allow you to fix the conflicts; after fixing conflicts, use <code class="literal">git add</code>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1073to update the index with those contents, and then, instead of
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1074running <code class="literal">git commit</code>, just run</p><pre class="literallayout">$ git rebase --continue</pre><p>and Git will continue applying the rest of the patches.</p><p>At any point you may use the <code class="literal">--abort</code> option to abort this process and
Junio C Hamano5dab5a92013-02-25 18:51:24[diff] [blame]1075return mywork to the state it had before you started the rebase:</p><pre class="literallayout">$ git rebase --abort</pre><p>If you need to reorder or edit a number of commits in a branch, it may
1076be easier to use <code class="literal">git rebase -i</code>, which allows you to reorder and
1077squash commits, as well as marking them for individual editing during
1078the rebase. See <a class="xref" href="#interactive-rebase" title="Using interactive rebases">the section called “Using interactive rebases”</a> for details, and
1079<a class="xref" href="#reordering-patch-series" title="Reordering or selecting from a patch series">the section called “Reordering or selecting from a patch series”</a> for alternatives.</p></div><div class="section" title="Rewriting a single commit"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="rewriting-one-commit"></a>Rewriting a single commit</h2></div></div></div><p>We saw in <a class="xref" href="#fixing-a-mistake-by-rewriting-history" title="Fixing a mistake by rewriting history">the section called “Fixing a mistake by rewriting history”</a> that you can replace the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1080most recent commit using</p><pre class="literallayout">$ git commit --amend</pre><p>which will replace the old commit by a new commit incorporating your
Junio C Hamano5dab5a92013-02-25 18:51:24[diff] [blame]1081changes, giving you a chance to edit the old commit message first.
1082This is useful for fixing typos in your last commit, or for adjusting
1083the patch contents of a poorly staged commit.</p><p>If you need to amend commits from deeper in your history, you can
1084use <a class="link" href="#interactive-rebase" title="Using interactive rebases">interactive rebase’s <code class="literal">edit</code> instruction</a>.</p></div><div class="section" title="Reordering or selecting from a patch series"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="reordering-patch-series"></a>Reordering or selecting from a patch series</h2></div></div></div><p>Sometimes you want to edit a commit deeper in your history. One
1085approach is to use <code class="literal">git format-patch</code> to create a series of patches
1086and then reset the state to before the patches:</p><pre class="literallayout">$ git format-patch origin
1087$ git reset --hard origin</pre><p>Then modify, reorder, or eliminate patches as needed before applying
1088them again with <a class="ulink" href="git-am.html" target="_top">git-am(1)</a>:</p><pre class="literallayout">$ git am *.patch</pre></div><div class="section" title="Using interactive rebases"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="interactive-rebase"></a>Using interactive rebases</h2></div></div></div><p>You can also edit a patch series with an interactive rebase. This is
1089the same as <a class="link" href="#reordering-patch-series" title="Reordering or selecting from a patch series">reordering a patch series using <code class="literal">format-patch</code></a>, so use whichever interface you like best.</p><p>Rebase your current HEAD on the last commit you want to retain as-is.
1090For example, if you want to reorder the last 5 commits, use:</p><pre class="literallayout">$ git rebase -i HEAD~5</pre><p>This will open your editor with a list of steps to be taken to perform
1091your rebase.</p><pre class="literallayout">pick deadbee The oneline of this commit
1092pick fa1afe1 The oneline of the next commit
1093...
1094
1095# Rebase c0ffeee..deadbee onto c0ffeee
1096#
1097# Commands:
1098# p, pick = use commit
1099# r, reword = use commit, but edit the commit message
1100# e, edit = use commit, but stop for amending
1101# s, squash = use commit, but meld into previous commit
1102# f, fixup = like "squash", but discard this commit's log message
1103# x, exec = run command (the rest of the line) using shell
1104#
1105# These lines can be re-ordered; they are executed from top to bottom.
1106#
1107# If you remove a line here THAT COMMIT WILL BE LOST.
1108#
1109# However, if you remove everything, the rebase will be aborted.
1110#
1111# Note that empty commits are commented out</pre><p>As explained in the comments, you can reorder commits, squash them
1112together, edit commit messages, etc. by editing the list. Once you
1113are satisfied, save the list and close your editor, and the rebase
1114will begin.</p><p>The rebase will stop where <code class="literal">pick</code> has been replaced with <code class="literal">edit</code> or
1115when a step in the list fails to mechanically resolve conflicts and
1116needs your help. When you are done editing and/or resolving conflicts
1117you can continue with <code class="literal">git rebase --continue</code>. If you decide that
1118things are getting too hairy, you can always bail out with <code class="literal">git rebase
1119--abort</code>. Even after the rebase is complete, you can still recover
1120the original branch by using the <a class="link" href="#reflogs" title="Reflogs">reflog</a>.</p><p>For a more detailed discussion of the procedure and additional tips,
1121see the "INTERACTIVE MODE" section of <a class="ulink" href="git-rebase.html" target="_top">git-rebase(1)</a>.</p></div><div class="section" title="Other tools"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="patch-series-tools"></a>Other tools</h2></div></div></div><p>There are numerous other tools, such as StGit, which exist for the
Junio C Hamanodb911ee2007-02-28 08:13:52[diff] [blame]1122purpose of maintaining a patch series. These are outside of the scope of
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1123this manual.</p></div><div class="section" title="Problems with rewriting history"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="problems-With-rewriting-history"></a>Problems with rewriting history</h2></div></div></div><p>The primary problem with rewriting the history of a branch has to do
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1124with merging. Suppose somebody fetches your branch and merges it into
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1125their branch, with a result something like this:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1126 \ \
1127 t--t--t--m &lt;-- their branch:</pre><p>Then suppose you modify the last three commits:</p><pre class="literallayout"> o--o--o &lt;-- new head of origin
1128 /
1129 o--o--O--o--o--o &lt;-- old head of origin</pre><p>If we examined all this history together in one repository, it will
1130look like:</p><pre class="literallayout"> o--o--o &lt;-- new head of origin
1131 /
1132 o--o--O--o--o--o &lt;-- old head of origin
1133 \ \
1134 t--t--t--m &lt;-- their branch:</pre><p>Git has no way of knowing that the new head is an updated version of
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1135the old head; it treats this situation exactly the same as it would if
1136two developers had independently done the work on the old and new heads
1137in parallel. At this point, if someone attempts to merge the new head
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1138in to their branch, Git will attempt to merge together the two (old and
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1139new) lines of development, instead of trying to replace the old by the
1140new. The results are likely to be unexpected.</p><p>You may still choose to publish branches whose history is rewritten,
1141and it may be useful for others to be able to fetch those branches in
1142order to examine or test them, but they should not attempt to pull such
1143branches into their own work.</p><p>For true distributed development that supports proper merging,
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1144published branches should never be rewritten.</p></div><div class="section" title="Why bisecting merge commits can be harder than bisecting linear history"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="bisect-merges"></a>Why bisecting merge commits can be harder than bisecting linear history</h2></div></div></div><p>The <a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> command correctly handles history that
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]1145includes merge commits. However, when the commit that it finds is a
1146merge commit, the user may need to work harder than usual to figure out
1147why that commit introduced a problem.</p><p>Imagine this history:</p><pre class="literallayout"> ---Z---o---X---...---o---A---C---D
1148 \ /
1149 o---o---Y---...---o---B</pre><p>Suppose that on the upper line of development, the meaning of one
1150of the functions that exists at Z is changed at commit X. The
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1151commits from Z leading to A change both the function’s
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]1152implementation and all calling sites that exist at Z, as well
1153as new calling sites they add, to be consistent. There is no
1154bug at A.</p><p>Suppose that in the meantime on the lower line of development somebody
1155adds a new calling site for that function at commit Y. The
1156commits from Z leading to B all assume the old semantics of that
1157function and the callers and the callee are consistent with each
1158other. There is no bug at B, either.</p><p>Suppose further that the two development lines merge cleanly at C,
1159so no conflict resolution is required.</p><p>Nevertheless, the code at C is broken, because the callers added
1160on the lower line of development have not been converted to the new
1161semantics introduced on the upper line of development. So if all
1162you know is that D is bad, that Z is good, and that
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1163<a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> identifies C as the culprit, how will you
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1164figure out that the problem is due to this change in semantics?</p><p>When the result of a <code class="literal">git bisect</code> is a non-merge commit, you should
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]1165normally be able to discover the problem by examining just that commit.
1166Developers can make this easy by breaking their changes into small
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1167self-contained commits. That won’t help in the case above, however,
1168because the problem isn’t obvious from examination of any single
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]1169commit; instead, a global view of the development is required. To
1170make matters worse, the change in semantics in the problematic
1171function may be just one small part of the changes in the upper
1172line of development.</p><p>On the other hand, if instead of merging at C you had rebased the
1173history between Z to B on top of A, you would have gotten this
1174linear history:</p><pre class="literallayout"> ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*</pre><p>Bisecting between Z and D* would hit a single culprit commit Y*,
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1175and understanding why Y* was broken would probably be easier.</p><p>Partly for this reason, many experienced Git users, even when
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]1176working on an otherwise merge-heavy project, keep the history
1177linear by rebasing against the latest upstream version before
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]1178publishing.</p></div></div><div class="chapter" title="Chapter 6. Advanced branch management"><div class="titlepage"><div><div><h2 class="title"><a name="advanced-branch-management"></a>Chapter 6. Advanced branch management</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#fetching-individual-branches">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fetch-fast-forwards">git fetch and fast-forwards</a></span></dt><dt><span class="section"><a href="#forcing-fetch">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#remote-branch-configuration">Configuring remote-tracking branches</a></span></dt></dl></div><div class="section" title="Fetching individual branches"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fetching-individual-branches"></a>Fetching individual branches</h2></div></div></div><p>Instead of using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>, you can also choose just
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1179to update one branch at a time, and to store it locally under an
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1180arbitrary name:</p><pre class="literallayout">$ git fetch origin todo:my-todo-work</pre><p>The first argument, <code class="literal">origin</code>, just tells Git to fetch from the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1181repository you originally cloned from. The second argument tells Git
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1182to fetch the branch named <code class="literal">todo</code> from the remote repository, and to
1183store it locally under the name <code class="literal">refs/heads/my-todo-work</code>.</p><p>You can also fetch branches from other repositories; so</p><pre class="literallayout">$ git fetch git://example.com/proj.git master:example-master</pre><p>will create a new branch named <code class="literal">example-master</code> and store in it the
1184branch named <code class="literal">master</code> from the repository at the given URL. If you
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1185already have a branch named example-master, it will attempt to
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1186<a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a> to the commit given by example.com’s
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1187master branch. In more detail:</p></div><div class="section" title="git fetch and fast-forwards"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fetch-fast-forwards"></a>git fetch and fast-forwards</h2></div></div></div><p>In the previous example, when updating an existing branch, <code class="literal">git fetch</code>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1188checks to make sure that the most recent commit on the remote
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1189branch is a descendant of the most recent commit on your copy of the
1190branch before updating your copy of the branch to point at the new
Junio C Hamano3f680f32009-11-16 02:10:54[diff] [blame]1191commit. Git calls this process a <a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a>.</p><p>A fast-forward looks something like this:</p><pre class="literallayout"> o--o--o--o &lt;-- old head of the branch
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1192 \
1193 o--o--o &lt;-- new head of the branch</pre><p>In some cases it is possible that the new head will <span class="strong"><strong>not</strong></span> actually be
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1194a descendant of the old head. For example, the developer may have
1195realized she made a serious mistake, and decided to backtrack,
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1196resulting in a situation like:</p><pre class="literallayout"> o--o--o--o--a--b &lt;-- old head of the branch
1197 \
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1198 o--o--o &lt;-- new head of the branch</pre><p>In this case, <code class="literal">git fetch</code> will fail, and print out a warning.</p><p>In that case, you can still force Git to update to the new head, as
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1199described in the following section. However, note that in the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1200situation above this may mean losing the commits labeled <code class="literal">a</code> and <code class="literal">b</code>,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1201unless you’ve already created a reference of your own pointing to
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1202them.</p></div><div class="section" title="Forcing git fetch to do non-fast-forward updates"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="forcing-fetch"></a>Forcing git fetch to do non-fast-forward updates</h2></div></div></div><p>If git fetch fails because the new head of a branch is not a
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1203descendant of the old head, you may force the update with:</p><pre class="literallayout">$ git fetch git://example.com/proj.git +master:refs/remotes/example/master</pre><p>Note the addition of the <code class="literal">+</code> sign. Alternatively, you can use the <code class="literal">-f</code>
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1204flag to force updates of all the fetched branches, as in:</p><pre class="literallayout">$ git fetch -f origin</pre><p>Be aware that commits that the old version of example/master pointed at
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1205may be lost, as we saw in the previous section.</p></div><div class="section" title="Configuring remote-tracking branches"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="remote-branch-configuration"></a>Configuring remote-tracking branches</h2></div></div></div><p>We saw above that <code class="literal">origin</code> is just a shortcut to refer to the
Junio C Hamanodb911ee2007-02-28 08:13:52[diff] [blame]1206repository that you originally cloned from. This information is
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1207stored in Git configuration variables, which you can see using
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1208<a class="ulink" href="git-config.html" target="_top">git-config(1)</a>:</p><pre class="literallayout">$ git config -l
1209core.repositoryformatversion=0
1210core.filemode=true
1211core.logallrefupdates=true
1212remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
1213remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
1214branch.master.remote=origin
1215branch.master.merge=refs/heads/master</pre><p>If there are other repositories that you also use frequently, you can
Junio C Hamano2da4ac42013-02-19 00:41:17[diff] [blame]1216create similar configuration options to save typing; for example,</p><pre class="literallayout">$ git remote add example git://example.com/proj.git</pre><p>adds the following to <code class="literal">.git/config</code>:</p><pre class="literallayout">[remote "example"]
1217 url = git://example.com/proj.git
1218 fetch = +refs/heads/*:refs/remotes/example/*</pre><p>Also note that the above configuration can be performed by directly
1219editing the file <code class="literal">.git/config</code> instead of using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>.</p><p>After configuring the remote, the following three commands will do the
1220same thing:</p><pre class="literallayout">$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/*
1221$ git fetch example +refs/heads/*:refs/remotes/example/*
1222$ git fetch example</pre><p>See <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for more details on the configuration
1223options mentioned above and <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> for more details on
1224the refspec syntax.</p></div></div><div class="chapter" title="Chapter 7. Git concepts"><div class="titlepage"><div><div><h2 class="title"><a name="git-concepts"></a>Chapter 7. Git concepts</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#the-object-database">The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="section"><a href="#the-index">The index</a></span></dt></dl></div><p>Git is built on a small number of simple but powerful ideas. While it
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1225is possible to get things done without understanding them, you will find
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1226Git much more intuitive if you do.</p><p>We start with the most important, the <a class="link" href="#def_object_database">object database</a> and the <a class="link" href="#def_index">index</a>.</p><div class="section" title="The Object Database"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="the-object-database"></a>The Object Database</h2></div></div></div><p>We already saw in <a class="xref" href="#understanding-commits" title="Understanding History: Commits">the section called “Understanding History: Commits”</a> that all commits are stored
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1227under a 40-digit "object name". In fact, all the information needed to
1228represent the history of a project is stored in objects with such names.
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1229In each case the name is calculated by taking the SHA-1 hash of the
1230contents of the object. The SHA-1 hash is a cryptographic hash function.
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1231What that means to us is that it is impossible to find two different
1232objects with the same name. This has a number of advantages; among
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1233others:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1234Git can quickly determine whether two objects are identical or not,
1235 just by comparing names.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1236</li><li class="listitem">
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1237Since object names are computed the same way in every repository, the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1238 same content stored in two repositories will always be stored under
1239 the same name.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1240</li><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1241Git can detect errors when it reads an object, by checking that the
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1242 object’s name is still the SHA-1 hash of its contents.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1243</li></ul></div><p>(See <a class="xref" href="#object-details" title="Object storage format">the section called “Object storage format”</a> for the details of the object formatting and
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1244SHA-1 calculation.)</p><p>There are four different types of objects: "blob", "tree", "commit", and
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1245"tag".</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1246A <a class="link" href="#def_blob_object">"blob" object</a> is used to store file data.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1247</li><li class="listitem">
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]1248A <a class="link" href="#def_tree_object">"tree" object</a> ties one or more
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1249 "blob" objects into a directory structure. In addition, a tree object
1250 can refer to other tree objects, thus creating a directory hierarchy.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1251</li><li class="listitem">
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1252A <a class="link" href="#def_commit_object">"commit" object</a> ties such directory hierarchies
1253 together into a <a class="link" href="#def_DAG">directed acyclic graph</a> of revisions—each
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1254 commit contains the object name of exactly one tree designating the
1255 directory hierarchy at the time of the commit. In addition, a commit
1256 refers to "parent" commit objects that describe the history of how we
1257 arrived at that directory hierarchy.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1258</li><li class="listitem">
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1259A <a class="link" href="#def_tag_object">"tag" object</a> symbolically identifies and can be
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1260 used to sign other objects. It contains the object name and type of
1261 another object, a symbolic name (of course!) and, optionally, a
1262 signature.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1263</li></ul></div><p>The object types in some more detail:</p><div class="section" title="Commit Object"><div class="titlepage"><div><div><h3 class="title"><a name="commit-object"></a>Commit Object</h3></div></div></div><p>The "commit" object links a physical state of a tree with a description
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1264of how we got there and why. Use the <code class="literal">--pretty=raw</code> option to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1265<a class="ulink" href="git-show.html" target="_top">git-show(1)</a> or <a class="ulink" href="git-log.html" target="_top">git-log(1)</a> to examine your favorite
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1266commit:</p><pre class="literallayout">$ git show -s --pretty=raw 2be7fcb476
1267commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
1268tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
1269parent 257a84d9d02e90447b149af58b271c19405edb6a
1270author Dave Watson &lt;dwatson@mimvista.com&gt; 1187576872 -0400
1271committer Junio C Hamano &lt;gitster@pobox.com&gt; 1187591163 -0700
1272
1273 Fix misspelling of 'suppress' in docs
1274
1275 Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;</pre><p>As you can see, a commit is defined by:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1276a tree: The SHA-1 name of a tree object (as defined below), representing
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1277 the contents of a directory at a certain point in time.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1278</li><li class="listitem">
Junio C Hamano44dcd492012-07-24 04:35:38[diff] [blame]1279parent(s): The SHA-1 name(s) of some number of commits which represent the
Junio C Hamano878cc1e2007-12-14 08:35:13[diff] [blame]1280 immediately previous step(s) in the history of the project. The
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1281 example above has one parent; merge commits may have more than
1282 one. A commit with no parents is called a "root" commit, and
1283 represents the initial revision of a project. Each project must have
1284 at least one root. A project can also have multiple roots, though
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1285 that isn’t common (or necessarily a good idea).
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1286</li><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1287an author: The name of the person responsible for this change, together
1288 with its date.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1289</li><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1290a committer: The name of the person who actually created the commit,
1291 with the date it was done. This may be different from the author, for
1292 example, if the author was someone who wrote a patch and emailed it
1293 to the person who used it to create the commit.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1294</li><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1295a comment describing this commit.
1296</li></ul></div><p>Note that a commit does not itself contain any information about what
1297actually changed; all changes are calculated by comparing the contents
1298of the tree referred to by this commit with the trees associated with
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1299its parents. In particular, Git does not attempt to record file renames
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1300explicitly, though it can identify cases where the existence of the same
1301file data at changing paths suggests a rename. (See, for example, the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1302<code class="literal">-M</code> option to <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>).</p><p>A commit is usually created by <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a>, which creates a
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1303commit whose parent is normally the current HEAD, and whose tree is
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1304taken from the content currently stored in the index.</p></div><div class="section" title="Tree Object"><div class="titlepage"><div><div><h3 class="title"><a name="tree-object"></a>Tree Object</h3></div></div></div><p>The ever-versatile <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> command can also be used to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1305examine tree objects, but <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a> will give you more
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1306details:</p><pre class="literallayout">$ git ls-tree fb3a8bdd0ce
1307100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
1308100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
1309100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
1310040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
1311100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
1312100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
1313100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
1314100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
1315...</pre><p>As you can see, a tree object contains a list of entries, each with a
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1316mode, object type, SHA-1 name, and name, sorted by name. It represents
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1317the contents of a single directory tree.</p><p>The object type may be a blob, representing the contents of a file, or
1318another tree, representing the contents of a subdirectory. Since trees
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1319and blobs, like all other objects, are named by the SHA-1 hash of their
1320contents, two trees have the same SHA-1 name if and only if their
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1321contents (including, recursively, the contents of all subdirectories)
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1322are identical. This allows Git to quickly determine the differences
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1323between two related tree objects, since it can ignore any entries with
1324identical object names.</p><p>(Note: in the presence of submodules, trees may also have commits as
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1325entries. See <a class="xref" href="#submodules" title="Chapter 8. Submodules">Chapter 8, <i>Submodules</i></a> for documentation.)</p><p>Note that the files all have mode 644 or 755: Git actually only pays
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1326attention to the executable bit.</p></div><div class="section" title="Blob Object"><div class="titlepage"><div><div><h3 class="title"><a name="blob-object"></a>Blob Object</h3></div></div></div><p>You can use <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> to examine the contents of a blob; take,
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1327for example, the blob in the entry for <code class="literal">COPYING</code> from the tree above:</p><pre class="literallayout">$ git show 6ff87c4664
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1328
1329 Note that the only valid version of the GPL as far as this project
1330 is concerned is _this_ particular version of the license (ie v2, not
1331 v2.2 or v3.x or whatever), unless explicitly otherwise stated.
1332...</pre><p>A "blob" object is nothing but a binary blob of data. It doesn’t refer
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1333to anything else or have attributes of any kind.</p><p>Since the blob is entirely defined by its data, if two files in a
1334directory tree (or in multiple different versions of the repository)
1335have the same contents, they will share the same blob object. The object
1336is totally independent of its location in the directory tree, and
1337renaming a file does not change the object that file is associated with.</p><p>Note that any tree or blob object can be examined using
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1338<a class="ulink" href="git-show.html" target="_top">git-show(1)</a> with the &lt;revision&gt;:&lt;path&gt; syntax. This can
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1339sometimes be useful for browsing the contents of a tree that is not
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1340currently checked out.</p></div><div class="section" title="Trust"><div class="titlepage"><div><div><h3 class="title"><a name="trust"></a>Trust</h3></div></div></div><p>If you receive the SHA-1 name of a blob from one source, and its contents
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1341from another (possibly untrusted) source, you can still trust that those
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1342contents are correct as long as the SHA-1 name agrees. This is because
1343the SHA-1 is designed so that it is infeasible to find different contents
1344that produce the same hash.</p><p>Similarly, you need only trust the SHA-1 name of a top-level tree object
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1345to trust the contents of the entire directory that it refers to, and if
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1346you receive the SHA-1 name of a commit from a trusted source, then you
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1347can easily verify the entire history of commits reachable through
1348parents of that commit, and all of those contents of the trees referred
1349to by those commits.</p><p>So to introduce some real trust in the system, the only thing you need
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1350to do is to digitally sign just <span class="emphasis"><em>one</em></span> special note, which includes the
1351name of a top-level commit. Your digital signature shows others
1352that you trust that commit, and the immutability of the history of
1353commits tells others that they can trust the whole history.</p><p>In other words, you can easily validate a whole archive by just
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1354sending out a single email that tells the people the name (SHA-1 hash)
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1355of the top commit, and digitally sign that email using something
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1356like GPG/PGP.</p><p>To assist in this, Git also provides the tag object…</p></div><div class="section" title="Tag Object"><div class="titlepage"><div><div><h3 class="title"><a name="tag-object"></a>Tag Object</h3></div></div></div><p>A tag object contains an object, object type, tag name, the name of the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1357person ("tagger") who created the tag, and a message, which may contain
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1358a signature, as can be seen using <a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a>:</p><pre class="literallayout">$ git cat-file tag v1.5.0
1359object 437b1b20df4b356c9342dac8d38849f24ef44f27
1360type commit
1361tag v1.5.0
1362tagger Junio C Hamano &lt;junkio@cox.net&gt; 1171411200 +0000
1363
1364GIT 1.5.0
1365-----BEGIN PGP SIGNATURE-----
1366Version: GnuPG v1.4.6 (GNU/Linux)
1367
1368iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui
1369nLE/L9aUXdWeTFPron96DLA=
1370=2E+0
1371-----END PGP SIGNATURE-----</pre><p>See the <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> command to learn how to create and verify tag
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1372objects. (Note that <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> can also be used to create
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1373"lightweight tags", which are not tag objects at all, but just simple
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1374references whose names begin with <code class="literal">refs/tags/</code>).</p></div><div class="section" title="How Git stores objects efficiently: pack files"><div class="titlepage"><div><div><h3 class="title"><a name="pack-files"></a>How Git stores objects efficiently: pack files</h3></div></div></div><p>Newly created objects are initially created in a file named after the
1375object’s SHA-1 hash (stored in <code class="literal">.git/objects</code>).</p><p>Unfortunately this system becomes inefficient once a project has a
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1376lot of objects. Try this on an old project:</p><pre class="literallayout">$ git count-objects
13776930 objects, 47620 kilobytes</pre><p>The first number is the number of objects which are kept in
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1378individual files. The second is the amount of space taken up by
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1379those "loose" objects.</p><p>You can save space and make Git faster by moving these loose objects in
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1380to a "pack file", which stores a group of objects in an efficient
1381compressed format; the details of how pack files are formatted can be
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1382found in <a class="ulink" href="technical/pack-format.html" target="_top">pack format</a>.</p><p>To put the loose objects into a pack, just run git repack:</p><pre class="literallayout">$ git repack
1383Counting objects: 6020, done.
1384Delta compression using up to 4 threads.
1385Compressing objects: 100% (6020/6020), done.
1386Writing objects: 100% (6020/6020), done.
1387Total 6020 (delta 4070), reused 0 (delta 0)</pre><p>This creates a single "pack file" in .git/objects/pack/
1388containing all currently unpacked objects. You can then run</p><pre class="literallayout">$ git prune</pre><p>to remove any of the "loose" objects that are now contained in the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1389pack. This will also remove any unreferenced objects (which may be
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1390created when, for example, you use <code class="literal">git reset</code> to remove a commit).
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1391You can verify that the loose objects are gone by looking at the
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1392<code class="literal">.git/objects</code> directory or by running</p><pre class="literallayout">$ git count-objects
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]13930 objects, 0 kilobytes</pre><p>Although the object files are gone, any commands that refer to those
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1394objects will work exactly as they did before.</p><p>The <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a> command performs packing, pruning, and more for
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1395you, so is normally the only high-level command you need.</p></div><div class="section" title="Dangling objects"><div class="titlepage"><div><div><h3 class="title"><a name="dangling-objects"></a>Dangling objects</h3></div></div></div><p>The <a class="ulink" href="git-fsck.html" target="_top">git-fsck(1)</a> command will sometimes complain about dangling
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1396objects. They are not a problem.</p><p>The most common cause of dangling objects is that you’ve rebased a
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1397branch, or you have pulled from somebody else who rebased a branch—see
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1398<a class="xref" href="#cleaning-up-history" title="Chapter 5. Rewriting history and maintaining patch series">Chapter 5, <i>Rewriting history and maintaining patch series</i></a>. In that case, the old head of the original
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1399branch still exists, as does everything it pointed to. The branch
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1400pointer itself just doesn’t, since you replaced it with another one.</p><p>There are also other situations that cause dangling objects. For
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1401example, a "dangling blob" may arise because you did a <code class="literal">git add</code> of a
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1402file, but then, before you actually committed it and made it part of the
1403bigger picture, you changed something else in that file and committed
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1404that <span class="strong"><strong>updated</strong></span> thing—the old state that you added originally ends up
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1405not being pointed to by any commit or tree, so it’s now a dangling blob
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1406object.</p><p>Similarly, when the "recursive" merge strategy runs, and finds that
1407there are criss-cross merges and thus more than one merge base (which is
1408fairly unusual, but it does happen), it will generate one temporary
1409midway tree (or possibly even more, if you had lots of criss-crossing
1410merges and more than two merge bases) as a temporary internal merge
1411base, and again, those are real objects, but the end result will not end
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1412up pointing to them, so they end up "dangling" in your repository.</p><p>Generally, dangling objects aren’t anything to worry about. They can
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1413even be very useful: if you screw something up, the dangling objects can
1414be how you recover your old tree (say, you did a rebase, and realized
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1415that you really didn’t want to—you can look at what dangling objects
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1416you have, and decide to reset your head to some old dangling state).</p><p>For commits, you can just use:</p><pre class="literallayout">$ gitk &lt;dangling-commit-sha-goes-here&gt; --not --all</pre><p>This asks for all the history reachable from the given commit but not
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1417from any branch, tag, or other reference. If you decide it’s something
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1418you want, you can always create a new reference to it, e.g.,</p><pre class="literallayout">$ git branch recovered-branch &lt;dangling-commit-sha-goes-here&gt;</pre><p>For blobs and trees, you can’t do the same, but you can still examine
1419them. You can just do</p><pre class="literallayout">$ git show &lt;dangling-blob/tree-sha-goes-here&gt;</pre><p>to show what the contents of the blob were (or, for a tree, basically
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1420what the <code class="literal">ls</code> for that directory was), and that may give you some idea
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1421of what the operation was that left that dangling object.</p><p>Usually, dangling blobs and trees aren’t very interesting. They’re
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1422almost always the result of either being a half-way mergebase (the blob
1423will often even have the conflict markers from a merge in it, if you
1424have had conflicting merges that you fixed up by hand), or simply
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1425because you interrupted a <code class="literal">git fetch</code> with ^C or something like that,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1426leaving <span class="emphasis"><em>some</em></span> of the new objects in the object database, but just
1427dangling and useless.</p><p>Anyway, once you are sure that you’re not interested in any dangling
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1428state, you can just prune all unreachable objects:</p><pre class="literallayout">$ git prune</pre><p>and they’ll be gone. (You should only run <code class="literal">git prune</code> on a quiescent
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1429repository—it’s kind of like doing a filesystem fsck recovery: you
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1430don’t want to do that while the filesystem is mounted.
1431<code class="literal">git prune</code> is designed not to cause any harm in such cases of concurrent
1432accesses to a repository but you might receive confusing or scary messages.)</p></div><div class="section" title="Recovering from repository corruption"><div class="titlepage"><div><div><h3 class="title"><a name="recovering-from-repository-corruption"></a>Recovering from repository corruption</h3></div></div></div><p>By design, Git treats data trusted to it with caution. However, even in
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1433the absence of bugs in Git itself, it is still possible that hardware or
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1434operating system errors could corrupt data.</p><p>The first defense against such problems is backups. You can back up a
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1435Git directory using clone, or just using cp, tar, or any other backup
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1436mechanism.</p><p>As a last resort, you can search for the corrupted objects and attempt
1437to replace them by hand. Back up your repository before attempting this
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1438in case you corrupt things even more in the process.</p><p>We’ll assume that the problem is a single missing or corrupted blob,
Junio C Hamano878cc1e2007-12-14 08:35:13[diff] [blame]1439which is sometimes a solvable problem. (Recovering missing trees and
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1440especially commits is <span class="strong"><strong>much</strong></span> harder).</p><p>Before starting, verify that there is corruption, and figure out where
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1441it is with <a class="ulink" href="git-fsck.html" target="_top">git-fsck(1)</a>; this may be time-consuming.</p><p>Assume the output looks like this:</p><pre class="literallayout">$ git fsck --full --no-dangling
1442broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
1443 to blob 4b9458b3786228369c63936db65827de3cc06200
1444missing blob 4b9458b3786228369c63936db65827de3cc06200</pre><p>Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1445points to it. If you could find just one copy of that missing blob
1446object, possibly in some other repository, you could move it into
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1447<code class="literal">.git/objects/4b/9458b3...</code> and be done. Suppose you can’t. You can
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1448still examine the tree that pointed to it with <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a>,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1449which might output something like:</p><pre class="literallayout">$ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
1450100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore
1451100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap
1452100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING
1453...
1454100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile
1455...</pre><p>So now you know that the missing blob was the data for a file named
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1456<code class="literal">myfile</code>. And chances are you can also identify the directory—let’s
1457say it’s in <code class="literal">somedirectory</code>. If you’re lucky the missing copy might be
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1458the same as the copy you have checked out in your working tree at
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1459<code class="literal">somedirectory/myfile</code>; you can test whether that’s right with
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1460<a class="ulink" href="git-hash-object.html" target="_top">git-hash-object(1)</a>:</p><pre class="literallayout">$ git hash-object -w somedirectory/myfile</pre><p>which will create and store a blob object with the contents of
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1461somedirectory/myfile, and output the SHA-1 of that object. if you’re
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1462extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1463which case you’ve guessed right, and the corruption is fixed!</p><p>Otherwise, you need more information. How do you tell which version of
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1464the file has been lost?</p><p>The easiest way to do this is with:</p><pre class="literallayout">$ git log --raw --all --full-history -- somedirectory/myfile</pre><p>Because you’re asking for raw output, you’ll now get something like</p><pre class="literallayout">commit abc
1465Author:
1466Date:
1467...
1468:100644 100644 4b9458b... newsha... M somedirectory/myfile
1469
1470
1471commit xyz
1472Author:
1473Date:
1474
1475...
1476:100644 100644 oldsha... 4b9458b... M somedirectory/myfile</pre><p>This tells you that the immediately following version of the file was
Junio C Hamano44dcd492012-07-24 04:35:38[diff] [blame]1477"newsha", and that the immediately preceding version was "oldsha".
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1478You also know the commit messages that went with the change from oldsha
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1479to 4b9458b and with the change from 4b9458b to newsha.</p><p>If you’ve been committing small enough changes, you may now have a good
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1480shot at reconstructing the contents of the in-between state 4b9458b.</p><p>If you can do that, you can now recreate the missing object with</p><pre class="literallayout">$ git hash-object -w &lt;recreated-file&gt;</pre><p>and your repository is good again!</p><p>(Btw, you could have ignored the <code class="literal">fsck</code>, and started with doing a</p><pre class="literallayout">$ git log --raw --all</pre><p>and just looked for the sha of the missing object (4b9458b..) in that
Junio C Hamano8c5696d2013-02-11 05:35:00[diff] [blame]1481whole thing. It’s up to you—Git does <span class="strong"><strong>have</strong></span> a lot of information, it is
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1482just missing one particular blob version.</p></div></div><div class="section" title="The index"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="the-index"></a>The index</h2></div></div></div><p>The index is a binary file (generally kept in <code class="literal">.git/index</code>) containing a
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1483sorted list of path names, each with permissions and the SHA-1 of a blob
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1484object; <a class="ulink" href="git-ls-files.html" target="_top">git-ls-files(1)</a> can show you the contents of the index:</p><pre class="literallayout">$ git ls-files --stage
1485100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore
1486100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap
1487100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING
1488100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore
1489100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile
1490...
1491100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h
1492100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c
1493100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h</pre><p>Note that in older documentation you may see the index called the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1494"current directory cache" or just the "cache". It has three important
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1495properties:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p class="simpara">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1496The index contains all the information necessary to generate a single
1497(uniquely determined) tree object.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1498</p><p class="simpara">For example, running <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a> generates this tree object
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1499from the index, stores it in the object database, and uses it as the
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1500tree object associated with the new commit.</p></li><li class="listitem"><p class="simpara">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1501The index enables fast comparisons between the tree object it defines
1502and the working tree.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1503</p><p class="simpara">It does this by storing some additional data for each entry (such as
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1504the last modified time). This data is not displayed above, and is not
1505stored in the created tree object, but it can be used to determine
1506quickly which files in the working directory differ from what was
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1507stored in the index, and thus save Git from having to read all of the
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1508data from such files to look for changes.</p></li><li class="listitem"><p class="simpara">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1509It can efficiently represent information about merge conflicts
1510between different tree objects, allowing each pathname to be
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1511associated with sufficient information about the trees involved that
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1512you can create a three-way merge between them.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1513</p><p class="simpara">We saw in <a class="xref" href="#conflict-resolution" title="Getting conflict-resolution help during a merge">the section called “Getting conflict-resolution help during a merge”</a> that during a merge the index can
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1514store multiple versions of a single file (called "stages"). The third
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1515column in the <a class="ulink" href="git-ls-files.html" target="_top">git-ls-files(1)</a> output above is the stage
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1516number, and will take on values other than 0 for files with merge
1517conflicts.</p></li></ol></div><p>The index is thus a sort of temporary staging area, which is filled with
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1518a tree which you are in the process of working on.</p><p>If you blow the index away entirely, you generally haven’t lost any
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1519information as long as you have the name of the tree that it described.</p></div></div><div class="chapter" title="Chapter 8. Submodules"><div class="titlepage"><div><div><h2 class="title"><a name="submodules"></a>Chapter 8. Submodules</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#_pitfalls_with_submodules">Pitfalls with submodules</a></span></dt></dl></div><p>Large projects are often composed of smaller, self-contained modules. For
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1520example, an embedded Linux distribution’s source tree would include every
Junio C Hamano4fd58d42007-09-30 00:51:14[diff] [blame]1521piece of software in the distribution with some local modifications; a movie
1522player might need to build against a specific, known-working version of a
1523decompression library; several independent programs might all share the same
1524build scripts.</p><p>With centralized revision control systems this is often accomplished by
1525including every module in one single repository. Developers can check out
1526all modules or only the modules they need to work with. They can even modify
1527files across several modules in a single commit while moving things around
1528or updating APIs and translations.</p><p>Git does not allow partial checkouts, so duplicating this approach in Git
1529would force developers to keep a local copy of modules they are not
1530interested in touching. Commits in an enormous checkout would be slower
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1531than you’d expect as Git would have to scan every directory for changes.
Junio C Hamano4fd58d42007-09-30 00:51:14[diff] [blame]1532If modules have a lot of local history, clones would take forever.</p><p>On the plus side, distributed revision control systems can much better
1533integrate with external sources. In a centralized model, a single arbitrary
1534snapshot of the external project is exported from its own revision control
1535and then imported into the local revision control on a vendor branch. All
1536the history is hidden. With distributed revision control you can clone the
1537entire external history and much more easily follow development and re-merge
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1538local changes.</p><p>Git’s submodule support allows a repository to contain, as a subdirectory, a
Junio C Hamano4fd58d42007-09-30 00:51:14[diff] [blame]1539checkout of an external project. Submodules maintain their own identity;
1540the submodule support just stores the submodule repository location and
1541commit ID, so other developers who clone the containing project
1542("superproject") can easily clone all the submodules at the same revision.
1543Partial checkouts of the superproject are possible: you can tell Git to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1544clone none, some or all of the submodules.</p><p>The <a class="ulink" href="git-submodule.html" target="_top">git-submodule(1)</a> command is available since Git 1.5.3. Users
Junio C Hamano4fd58d42007-09-30 00:51:14[diff] [blame]1545with Git 1.5.2 can look up the submodule commits in the repository and
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1546manually check them out; earlier versions won’t recognize the submodules at
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1547all.</p><p>To see how submodule support works, create four example
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1548repositories that can be used later as a submodule:</p><pre class="literallayout">$ mkdir ~/git
1549$ cd ~/git
1550$ for i in a b c d
1551do
1552 mkdir $i
1553 cd $i
1554 git init
1555 echo "module $i" &gt; $i.txt
1556 git add $i.txt
1557 git commit -m "Initial commit, submodule $i"
1558 cd ..
1559done</pre><p>Now create the superproject and add all the submodules:</p><pre class="literallayout">$ mkdir super
1560$ cd super
1561$ git init
1562$ for i in a b c d
1563do
1564 git submodule add ~/git/$i $i
1565done</pre><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Do not use local URLs here if you plan to publish your superproject!</p></div><p>See what files <code class="literal">git submodule</code> created:</p><pre class="literallayout">$ ls -a
1566. .. .git .gitmodules a b c d</pre><p>The <code class="literal">git submodule add &lt;repo&gt; &lt;path&gt;</code> command does a couple of things:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1567It clones the submodule from <code class="literal">&lt;repo&gt;</code> to the given <code class="literal">&lt;path&gt;</code> under the
Junio C Hamano7f80ae82008-07-30 18:31:35[diff] [blame]1568 current directory and by default checks out the master branch.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1569</li><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1570It adds the submodule’s clone path to the <a class="ulink" href="gitmodules.html" target="_top">gitmodules(5)</a> file and
Junio C Hamano4fd58d42007-09-30 00:51:14[diff] [blame]1571 adds this file to the index, ready to be committed.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1572</li><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1573It adds the submodule’s current commit ID to the index, ready to be
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1574 committed.
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1575</li></ul></div><p>Commit the superproject:</p><pre class="literallayout">$ git commit -m "Add submodules a, b, c and d."</pre><p>Now clone the superproject:</p><pre class="literallayout">$ cd ..
1576$ git clone super cloned
1577$ cd cloned</pre><p>The submodule directories are there, but they’re empty:</p><pre class="literallayout">$ ls -a a
1578. ..
1579$ git submodule status
1580-d266b9873ad50488163457f025db7cdd9683d88b a
1581-e81d457da15309b4fef4249aba9b50187999670d b
1582-c1536a972b9affea0f16e0680ba87332dc059146 c
1583-d96249ff5d57de5de093e6baff9e0aafa5276a74 d</pre><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>The commit object names shown above would be different for you, but they
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1584should match the HEAD commit object names of your repositories. You can check
1585it by running <code class="literal">git ls-remote ../a</code>.</p></div><p>Pulling down the submodules is a two-step process. First run <code class="literal">git submodule
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1586init</code> to add the submodule repository URLs to <code class="literal">.git/config</code>:</p><pre class="literallayout">$ git submodule init</pre><p>Now use <code class="literal">git submodule update</code> to clone the repositories and check out the
1587commits specified in the superproject:</p><pre class="literallayout">$ git submodule update
1588$ cd a
1589$ ls -a
1590. .. .git a.txt</pre><p>One major difference between <code class="literal">git submodule update</code> and <code class="literal">git submodule add</code> is
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1591that <code class="literal">git submodule update</code> checks out a specific commit, rather than the tip
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1592of a branch. It’s like checking out a tag: the head is detached, so you’re not
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1593working on a branch.</p><pre class="literallayout">$ git branch
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1594* (detached from d266b98)
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1595 master</pre><p>If you want to make a change within a submodule and you have a detached head,
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1596then you should create or checkout a branch, make your changes, publish the
1597change within the submodule, and then update the superproject to reference the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1598new commit:</p><pre class="literallayout">$ git checkout master</pre><p>or</p><pre class="literallayout">$ git checkout -b fix-up</pre><p>then</p><pre class="literallayout">$ echo "adding a line again" &gt;&gt; a.txt
1599$ git commit -a -m "Updated the submodule from within the superproject."
1600$ git push
1601$ cd ..
1602$ git diff
1603diff --git a/a b/a
1604index d266b98..261dfac 160000
1605--- a/a
1606+++ b/a
1607@@ -1 +1 @@
1608-Subproject commit d266b9873ad50488163457f025db7cdd9683d88b
1609+Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24
1610$ git add a
1611$ git commit -m "Updated submodule a."
1612$ git push</pre><p>You have to run <code class="literal">git submodule update</code> after <code class="literal">git pull</code> if you want to update
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1613submodules, too.</p><div class="section" title="Pitfalls with submodules"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_pitfalls_with_submodules"></a>Pitfalls with submodules</h2></div></div></div><p>Always publish the submodule change before publishing the change to the
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1614superproject that references it. If you forget to publish the submodule change,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1615others won’t be able to clone the repository:</p><pre class="literallayout">$ cd ~/git/super/a
1616$ echo i added another line to this file &gt;&gt; a.txt
1617$ git commit -a -m "doing it wrong this time"
1618$ cd ..
1619$ git add a
1620$ git commit -m "Updated submodule a again."
1621$ git push
1622$ cd ~/git/cloned
1623$ git pull
1624$ git submodule update
1625error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git.
1626Did you forget to 'git add'?
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1627Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a'</pre><p>In older Git versions it could be easily forgotten to commit new or modified
Junio C Hamano2b186d82010-02-02 07:17:34[diff] [blame]1628files in a submodule, which silently leads to similar problems as not pushing
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1629the submodule changes. Starting with Git 1.7.0 both <code class="literal">git status</code> and <code class="literal">git diff</code>
Junio C Hamano2b186d82010-02-02 07:17:34[diff] [blame]1630in the superproject show submodules as modified when they contain new or
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1631modified files to protect against accidentally committing such a state. <code class="literal">git
1632diff</code> will also add a <code class="literal">-dirty</code> to the work tree side when generating patch
1633output or used with the <code class="literal">--submodule</code> option:</p><pre class="literallayout">$ git diff
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1634diff --git a/sub b/sub
1635--- a/sub
1636+++ b/sub
1637@@ -1 +1 @@
1638-Subproject commit 3f356705649b5d566d97ff843cf193359229a453
1639+Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty
1640$ git diff --submodule
1641Submodule sub 3f35670..3f35670-dirty:</pre><p>You also should not rewind branches in a submodule beyond commits that were
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1642ever recorded in any superproject.</p><p>It’s not safe to run <code class="literal">git submodule update</code> if you’ve made and committed
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1643changes within a submodule without checking out a branch first. They will be
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1644silently overwritten:</p><pre class="literallayout">$ cat a.txt
1645module a
1646$ echo line added from private2 &gt;&gt; a.txt
1647$ git commit -a -m "line added inside private2"
1648$ cd ..
1649$ git submodule update
1650Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b'
1651$ cd a
1652$ cat a.txt
Junio C Hamano5dab5a92013-02-25 18:51:24[diff] [blame]1653module a</pre><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>The changes are still visible in the submodule’s reflog.</p></div><p>If you have uncommitted changes in your submodule working tree, <code class="literal">git
1654submodule update</code> will not overwrite them. Instead, you get the usual
1655warning about not being able switch from a dirty branch.</p></div></div><div class="chapter" title="Chapter 9. Low-level Git operations"><div class="titlepage"><div><div><h2 class="title"><a name="low-level-operations"></a>Chapter 9. Low-level Git operations</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#object-manipulation">Object access and manipulation</a></span></dt><dt><span class="section"><a href="#the-workflow">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#examining-the-data">Examining the data</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#merging-multiple-trees-2">Merging multiple trees, continued</a></span></dt></dl></div><p>Many of the higher-level commands were originally implemented as shell
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1656scripts using a smaller core of low-level Git commands. These can still
1657be useful when doing unusual things with Git, or just as a way to
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1658understand its inner workings.</p><div class="section" title="Object access and manipulation"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="object-manipulation"></a>Object access and manipulation</h2></div></div></div><p>The <a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a> command can show the contents of any object,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1659though the higher-level <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> is usually more useful.</p><p>The <a class="ulink" href="git-commit-tree.html" target="_top">git-commit-tree(1)</a> command allows constructing commits with
1660arbitrary parents and trees.</p><p>A tree can be created with <a class="ulink" href="git-write-tree.html" target="_top">git-write-tree(1)</a> and its data can be
1661accessed by <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a>. Two trees can be compared with
1662<a class="ulink" href="git-diff-tree.html" target="_top">git-diff-tree(1)</a>.</p><p>A tag is created with <a class="ulink" href="git-mktag.html" target="_top">git-mktag(1)</a>, and the signature can be
1663verified by <a class="ulink" href="git-verify-tag.html" target="_top">git-verify-tag(1)</a>, though it is normally simpler to
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1664use <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> for both.</p></div><div class="section" title="The Workflow"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="the-workflow"></a>The Workflow</h2></div></div></div><p>High-level operations such as <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a>,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1665<a class="ulink" href="git-checkout.html" target="_top">git-checkout(1)</a> and <a class="ulink" href="git-reset.html" target="_top">git-reset(1)</a> work by moving data
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1666between the working tree, the index, and the object database. Git
1667provides low-level operations which perform each of these steps
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1668individually.</p><p>Generally, all Git operations work on the index file. Some operations
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1669work <span class="strong"><strong>purely</strong></span> on the index file (showing the current state of the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1670index), but most operations move data between the index file and either
1671the database or the working directory. Thus there are four main
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1672combinations:</p><div class="section" title="working directory → index"><div class="titlepage"><div><div><h3 class="title"><a name="working-directory-to-index"></a>working directory → index</h3></div></div></div><p>The <a class="ulink" href="git-update-index.html" target="_top">git-update-index(1)</a> command updates the index with
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1673information from the working directory. You generally update the
1674index information by just specifying the filename you want to update,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1675like so:</p><pre class="literallayout">$ git update-index filename</pre><p>but to avoid common mistakes with filename globbing etc, the command
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1676will not normally add totally new entries or remove old entries,
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1677i.e. it will normally just update existing cache entries.</p><p>To tell Git that yes, you really do realize that certain files no
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1678longer exist, or that new files should be added, you
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1679should use the <code class="literal">--remove</code> and <code class="literal">--add</code> flags respectively.</p><p>NOTE! A <code class="literal">--remove</code> flag does <span class="emphasis"><em>not</em></span> mean that subsequent filenames will
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1680necessarily be removed: if the files still exist in your directory
1681structure, the index will be updated with their new status, not
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1682removed. The only thing <code class="literal">--remove</code> means is that update-index will be
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1683considering a removed file to be a valid thing, and if the file really
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1684does not exist any more, it will update the index accordingly.</p><p>As a special case, you can also do <code class="literal">git update-index --refresh</code>, which
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1685will refresh the "stat" information of each index to match the current
1686stat information. It will <span class="emphasis"><em>not</em></span> update the object status itself, and
1687it will only update the fields that are used to quickly test whether
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1688an object still matches its old backing store object.</p><p>The previously introduced <a class="ulink" href="git-add.html" target="_top">git-add(1)</a> is just a wrapper for
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1689<a class="ulink" href="git-update-index.html" target="_top">git-update-index(1)</a>.</p></div><div class="section" title="index → object database"><div class="titlepage"><div><div><h3 class="title"><a name="index-to-object-database"></a>index → object database</h3></div></div></div><p>You write your current index file to a "tree" object with the program</p><pre class="literallayout">$ git write-tree</pre><p>that doesn’t come with any options—it will just write out the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1690current index into the set of tree objects that describe that state,
1691and it will return the name of the resulting top-level tree. You can
1692use that tree to re-generate the index at any time by going in the
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1693other direction:</p></div><div class="section" title="object database → index"><div class="titlepage"><div><div><h3 class="title"><a name="object-database-to-index"></a>object database → index</h3></div></div></div><p>You read a "tree" file from the object database, and use that to
1694populate (and overwrite—don’t do this if your index contains any
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1695unsaved state that you might want to restore later!) your current
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1696index. Normal operation is just</p><pre class="literallayout">$ git read-tree &lt;SHA-1 of tree&gt;</pre><p>and your index file will now be equivalent to the tree that you saved
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1697earlier. However, that is only your <span class="emphasis"><em>index</em></span> file: your working
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1698directory contents have not been modified.</p></div><div class="section" title="index → working directory"><div class="titlepage"><div><div><h3 class="title"><a name="index-to-working-directory"></a>index → working directory</h3></div></div></div><p>You update your working directory from the index by "checking out"
1699files. This is not a very common operation, since normally you’d just
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1700keep your files updated, and rather than write to your working
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1701directory, you’d tell the index files about the changes in your
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1702working directory (i.e. <code class="literal">git update-index</code>).</p><p>However, if you decide to jump to a new version, or check out somebody
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1703else’s version, or just restore a previous tree, you’d populate your
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1704index file with read-tree, and then you need to check out the result
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1705with</p><pre class="literallayout">$ git checkout-index filename</pre><p>or, if you want to check out all of the index, use <code class="literal">-a</code>.</p><p>NOTE! <code class="literal">git checkout-index</code> normally refuses to overwrite old files, so
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1706if you have an old version of the tree already checked out, you will
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1707need to use the <code class="literal">-f</code> flag (<span class="emphasis"><em>before</em></span> the <code class="literal">-a</code> flag or the filename) to
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1708<span class="emphasis"><em>force</em></span> the checkout.</p><p>Finally, there are a few odds and ends which are not purely moving
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1709from one representation to the other:</p></div><div class="section" title="Tying it all together"><div class="titlepage"><div><div><h3 class="title"><a name="tying-it-all-together"></a>Tying it all together</h3></div></div></div><p>To commit a tree you have instantiated with <code class="literal">git write-tree</code>, you’d
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1710create a "commit" object that refers to that tree and the history
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1711behind it—most notably the "parent" commits that preceded it in
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1712history.</p><p>Normally a "commit" has one parent: the previous state of the tree
1713before a certain change was made. However, sometimes it can have two
1714or more parent commits, in which case we call it a "merge", due to the
1715fact that such a commit brings together ("merges") two or more
1716previous states represented by other commits.</p><p>In other words, while a "tree" represents a particular directory state
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1717of a working directory, a "commit" represents that state in time,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1718and explains how we got there.</p><p>You create a commit object by giving it the tree that describes the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1719state at the time of the commit, and a list of parents:</p><pre class="literallayout">$ git commit-tree &lt;tree&gt; -p &lt;parent&gt; [(-p &lt;parent2&gt;)...]</pre><p>and then giving the reason for the commit on stdin (either through
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1720redirection from a pipe or file, or by just typing it at the tty).</p><p><code class="literal">git commit-tree</code> will return the name of the object that represents
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1721that commit, and you should save it away for later use. Normally,
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1722you’d commit a new <code class="literal">HEAD</code> state, and while Git doesn’t care where you
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1723save the note about that state, in practice we tend to just write the
1724result to the file pointed at by <code class="literal">.git/HEAD</code>, so that we can always see
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1725what the last committed state was.</p><p>Here is a picture that illustrates how various pieces fit together:</p><pre class="literallayout"> commit-tree
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1726 commit obj
1727 +----+
1728 | |
1729 | |
1730 V V
1731 +-----------+
1732 | Object DB |
1733 | Backing |
1734 | Store |
1735 +-----------+
1736 ^
1737 write-tree | |
1738 tree obj | |
1739 | | read-tree
1740 | | tree obj
1741 V
1742 +-----------+
1743 | Index |
1744 | "cache" |
1745 +-----------+
1746 update-index ^
1747 blob obj | |
1748 | |
1749 checkout-index -u | | checkout-index
1750 stat | | blob obj
1751 V
1752 +-----------+
1753 | Working |
1754 | Directory |
1755 +-----------+</pre></div></div><div class="section" title="Examining the data"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="examining-the-data"></a>Examining the data</h2></div></div></div><p>You can examine the data represented in the object database and the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1756index with various helper tools. For every object, you can use
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1757<a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a> to examine details about the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1758object:</p><pre class="literallayout">$ git cat-file -t &lt;objectname&gt;</pre><p>shows the type of the object, and once you have the type (which is
1759usually implicit in where you find the object), you can use</p><pre class="literallayout">$ git cat-file blob|tree|commit|tag &lt;objectname&gt;</pre><p>to show its contents. NOTE! Trees have binary content, and as a result
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1760there is a special helper for showing that content, called
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1761<code class="literal">git ls-tree</code>, which turns the binary content into a more easily
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1762readable form.</p><p>It’s especially instructive to look at "commit" objects, since those
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1763tend to be small and fairly self-explanatory. In particular, if you
1764follow the convention of having the top commit name in <code class="literal">.git/HEAD</code>,
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1765you can do</p><pre class="literallayout">$ git cat-file commit HEAD</pre><p>to see what the top commit was.</p></div><div class="section" title="Merging multiple trees"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging-multiple-trees"></a>Merging multiple trees</h2></div></div></div><p>Git can help you perform a three-way merge, which can in turn be
1766used for a many-way merge by repeating the merge procedure several
1767times. The usual situation is that you only do one three-way merge
1768(reconciling two lines of history) and commit the result, but if
1769you like to, you can merge several branches in one go.</p><p>To perform a three-way merge, you start with the two commits you
1770want to merge, find their closest common parent (a third commit),
1771and compare the trees corresponding to these three commits.</p><p>To get the "base" for the merge, look up the common parent of two
1772commits:</p><pre class="literallayout">$ git merge-base &lt;commit1&gt; &lt;commit2&gt;</pre><p>This prints the name of a commit they are both based on. You should
1773now look up the tree objects of those commits, which you can easily
1774do with</p><pre class="literallayout">$ git cat-file commit &lt;commitname&gt; | head -1</pre><p>since the tree object information is always the first line in a commit
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1775object.</p><p>Once you know the three trees you are going to merge (the one "original"
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]1776tree, aka the common tree, and the two "result" trees, aka the branches
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1777you want to merge), you do a "merge" read into the index. This will
1778complain if it has to throw away your old index contents, so you should
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1779make sure that you’ve committed those—in fact you would normally
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1780always do a merge against your last commit (which should thus match what
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1781you have in your current index anyway).</p><p>To do the merge, do</p><pre class="literallayout">$ git read-tree -m -u &lt;origtree&gt; &lt;yourtree&gt; &lt;targettree&gt;</pre><p>which will do all trivial merge operations for you directly in the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1782index file, and you can just write the result out with
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1783<code class="literal">git write-tree</code>.</p></div><div class="section" title="Merging multiple trees, continued"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging-multiple-trees-2"></a>Merging multiple trees, continued</h2></div></div></div><p>Sadly, many merges aren’t trivial. If there are files that have
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1784been added, moved or removed, or if both branches have modified the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1785same file, you will be left with an index tree that contains "merge
1786entries" in it. Such an index tree can <span class="emphasis"><em>NOT</em></span> be written out to a tree
1787object, and you will have to resolve any such merge clashes using
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1788other tools before you can write out the result.</p><p>You can examine such index state with <code class="literal">git ls-files --unmerged</code>
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1789command. An example:</p><pre class="literallayout">$ git read-tree -m $orig HEAD $target
1790$ git ls-files --unmerged
1791100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
1792100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
1793100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c</pre><p>Each line of the <code class="literal">git ls-files --unmerged</code> output begins with
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1794the blob mode bits, blob SHA-1, <span class="emphasis"><em>stage number</em></span>, and the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1795filename. The <span class="emphasis"><em>stage number</em></span> is Git’s way to say which tree it
Junio C Hamano44dcd492012-07-24 04:35:38[diff] [blame]1796came from: stage 1 corresponds to the <code class="literal">$orig</code> tree, stage 2 to
1797the <code class="literal">HEAD</code> tree, and stage 3 to the <code class="literal">$target</code> tree.</p><p>Earlier we said that trivial merges are done inside
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1798<code class="literal">git read-tree -m</code>. For example, if the file did not change
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1799from <code class="literal">$orig</code> to <code class="literal">HEAD</code> nor <code class="literal">$target</code>, or if the file changed
1800from <code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> the same way,
1801obviously the final outcome is what is in <code class="literal">HEAD</code>. What the
1802above example shows is that file <code class="literal">hello.c</code> was changed from
1803<code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> in a different way.
1804You could resolve this by running your favorite 3-way merge
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1805program, e.g. <code class="literal">diff3</code>, <code class="literal">merge</code>, or Git’s own merge-file, on
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1806the blob objects from these three stages yourself, like this:</p><pre class="literallayout">$ git cat-file blob 263414f... &gt;hello.c~1
1807$ git cat-file blob 06fa6a2... &gt;hello.c~2
1808$ git cat-file blob cc44c73... &gt;hello.c~3
1809$ git merge-file hello.c~2 hello.c~1 hello.c~3</pre><p>This would leave the merge result in <code class="literal">hello.c~2</code> file, along
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1810with conflict markers if there are conflicts. After verifying
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1811the merge result makes sense, you can tell Git what the final
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1812merge result for this file is by:</p><pre class="literallayout">$ mv -f hello.c~2 hello.c
1813$ git update-index hello.c</pre><p>When a path is in the "unmerged" state, running <code class="literal">git update-index</code> for
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1814that path tells Git to mark the path resolved.</p><p>The above is the description of a Git merge at the lowest level,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1815to help you understand what conceptually happens under the hood.
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1816In practice, nobody, not even Git itself, runs <code class="literal">git cat-file</code> three times
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1817for this. There is a <code class="literal">git merge-index</code> program that extracts the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1818stages to temporary files and calls a "merge" script on it:</p><pre class="literallayout">$ git merge-index git-merge-one-file hello.c</pre><p>and that is what higher level <code class="literal">git merge -s resolve</code> is implemented with.</p></div></div><div class="chapter" title="Chapter 10. Hacking Git"><div class="titlepage"><div><div><h2 class="title"><a name="hacking-git"></a>Chapter 10. Hacking Git</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#object-details">Object storage format</a></span></dt><dt><span class="section"><a href="#birdview-on-the-source-code">A birds-eye view of Git’s source code</a></span></dt></dl></div><p>This chapter covers internal details of the Git implementation which
1819probably only Git developers need to understand.</p><div class="section" title="Object storage format"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="object-details"></a>Object storage format</h2></div></div></div><p>All objects have a statically determined "type" which identifies the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1820format of the object (i.e. how it is used, and how it can refer to other
1821objects). There are currently four different object types: "blob",
1822"tree", "commit", and "tag".</p><p>Regardless of object type, all objects share the following
1823characteristics: they are all deflated with zlib, and have a header
1824that not only specifies their type, but also provides size information
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1825about the data in the object. It’s worth noting that the SHA-1 hash
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1826that is used to name the object is the hash of the original data
1827plus this header, so <code class="literal">sha1sum</code> <span class="emphasis"><em>file</em></span> does not match the object name
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]1828for <span class="emphasis"><em>file</em></span>.</p><p>As a result, the general consistency of an object can always be tested
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1829independently of the contents or the type of the object: all objects can
1830be validated by verifying that (a) their hashes match the content of the
1831file and (b) the object successfully inflates to a stream of bytes that
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]1832forms a sequence of
1833<code class="literal">&lt;ascii type without space&gt; + &lt;space&gt; + &lt;ascii decimal size&gt; +
1834&lt;byte\0&gt; + &lt;binary object data&gt;</code>.</p><p>The structured objects can further have their structure and
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1835connectivity to other objects verified. This is generally done with
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1836the <code class="literal">git fsck</code> program, which generates a full dependency graph
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1837of all objects, and verifies their internal consistency (in addition
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1838to just verifying their superficial consistency through the hash).</p></div><div class="section" title="A birds-eye view of Git’s source code"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="birdview-on-the-source-code"></a>A birds-eye view of Git’s source code</h2></div></div></div><p>It is not always easy for new developers to find their way through Git’s
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1839source code. This section gives you a little guidance to show where to
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1840start.</p><p>A good place to start is with the contents of the initial commit, with:</p><pre class="literallayout">$ git checkout e83c5163</pre><p>The initial revision lays the foundation for almost everything Git has
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1841today, but is small enough to read in one sitting.</p><p>Note that terminology has changed since that revision. For example, the
1842README in that revision uses the word "changeset" to describe what we
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]1843now call a <a class="link" href="#def_commit_object">commit</a>.</p><p>Also, we do not call it "cache" any more, but rather "index"; however, the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1844file is still called <code class="literal">cache.h</code>. Remark: Not much reason to change it now,
1845especially since there is no good single name for it anyway, because it is
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1846basically <span class="emphasis"><em>the</em></span> header file which is included by <span class="emphasis"><em>all</em></span> of Git’s C sources.</p><p>If you grasp the ideas in that initial commit, you should check out a
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1847more recent version and skim <code class="literal">cache.h</code>, <code class="literal">object.h</code> and <code class="literal">commit.h</code>.</p><p>In the early days, Git (in the tradition of UNIX) was a bunch of programs
1848which were extremely simple, and which you used in scripts, piping the
1849output of one into another. This turned out to be good for initial
1850development, since it was easier to test new things. However, recently
1851many of these parts have become builtins, and some of the core has been
1852"libified", i.e. put into libgit.a for performance, portability reasons,
1853and to avoid code duplication.</p><p>By now, you know what the index is (and find the corresponding data
1854structures in <code class="literal">cache.h</code>), and that there are just a couple of object types
1855(blobs, trees, commits and tags) which inherit their common structure from
1856<code class="literal">struct object</code>, which is their first member (and thus, you can cast e.g.
Junio C Hamanob76a6862012-05-02 22:02:46[diff] [blame]1857<code class="literal">(struct object *)commit</code> to achieve the <span class="emphasis"><em>same</em></span> as <code class="literal">&amp;commit-&gt;object</code>, i.e.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1858get at the object name and flags).</p><p>Now is a good point to take a break to let this information sink in.</p><p>Next step: get familiar with the object naming. Read <a class="xref" href="#naming-commits" title="Naming commits">the section called “Naming commits”</a>.
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1859There are quite a few ways to name an object (and not only revisions!).
1860All of these are handled in <code class="literal">sha1_name.c</code>. Just have a quick look at
1861the function <code class="literal">get_sha1()</code>. A lot of the special handling is done by
1862functions like <code class="literal">get_sha1_basic()</code> or the likes.</p><p>This is just to get you into the groove for the most libified part of Git:
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1863the revision walker.</p><p>Basically, the initial version of <code class="literal">git log</code> was a shell script:</p><pre class="literallayout">$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \
1864 LESS=-S ${PAGER:-less}</pre><p>What does this mean?</p><p><code class="literal">git rev-list</code> is the original version of the revision walker, which
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1865<span class="emphasis"><em>always</em></span> printed a list of revisions to stdout. It is still functional,
Junio C Hamano27a128b2009-08-13 01:23:00[diff] [blame]1866and needs to, since most new Git commands start out as scripts using
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1867<code class="literal">git rev-list</code>.</p><p><code class="literal">git rev-parse</code> is not as important any more; it was only used to filter out
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1868options that were relevant for the different plumbing commands that were
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1869called by the script.</p><p>Most of what <code class="literal">git rev-list</code> did is contained in <code class="literal">revision.c</code> and
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1870<code class="literal">revision.h</code>. It wraps the options in a struct named <code class="literal">rev_info</code>, which
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1871controls how and what revisions are walked, and more.</p><p>The original job of <code class="literal">git rev-parse</code> is now taken by the function
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1872<code class="literal">setup_revisions()</code>, which parses the revisions and the common command line
1873options for the revision walker. This information is stored in the struct
1874<code class="literal">rev_info</code> for later consumption. You can do your own command line option
1875parsing after calling <code class="literal">setup_revisions()</code>. After that, you have to call
1876<code class="literal">prepare_revision_walk()</code> for initialization, and then you can get the
1877commits one by one with the function <code class="literal">get_revision()</code>.</p><p>If you are interested in more details of the revision walking process,
1878just have a look at the first implementation of <code class="literal">cmd_log()</code>; call
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1879<code class="literal">git show v1.3.0~155^2~4</code> and scroll down to that function (note that you
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1880no longer need to call <code class="literal">setup_pager()</code> directly).</p><p>Nowadays, <code class="literal">git log</code> is a builtin, which means that it is <span class="emphasis"><em>contained</em></span> in the
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1881command <code class="literal">git</code>. The source side of a builtin is</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]1882a function called <code class="literal">cmd_&lt;bla&gt;</code>, typically defined in <code class="literal">builtin/&lt;bla.c&gt;</code>
1883 (note that older versions of Git used to have it in <code class="literal">builtin-&lt;bla&gt;.c</code>
1884 instead), and declared in <code class="literal">builtin.h</code>.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1885</li><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1886an entry in the <code class="literal">commands[]</code> array in <code class="literal">git.c</code>, and
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1887</li><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1888an entry in <code class="literal">BUILTIN_OBJECTS</code> in the <code class="literal">Makefile</code>.
1889</li></ul></div><p>Sometimes, more than one builtin is contained in one source file. For
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]1890example, <code class="literal">cmd_whatchanged()</code> and <code class="literal">cmd_log()</code> both reside in <code class="literal">builtin/log.c</code>,
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1891since they share quite a bit of code. In that case, the commands which are
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1892<span class="emphasis"><em>not</em></span> named like the <code class="literal">.c</code> file in which they live have to be listed in
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1893<code class="literal">BUILT_INS</code> in the <code class="literal">Makefile</code>.</p><p><code class="literal">git log</code> looks more complicated in C than it does in the original script,
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1894but that allows for a much greater flexibility and performance.</p><p>Here again it is a good point to take a pause.</p><p>Lesson three is: study the code. Really, it is the best way to learn about
1895the organization of Git (after you know the basic concepts).</p><p>So, think about something which you are interested in, say, "how can I
1896access a blob just knowing the object name of it?". The first step is to
1897find a Git command with which you can do it. In this example, it is either
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1898<code class="literal">git show</code> or <code class="literal">git cat-file</code>.</p><p>For the sake of clarity, let’s stay with <code class="literal">git cat-file</code>, because it</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1899is plumbing, and
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1900</li><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1901was around even in the initial commit (it literally went only through
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]1902 some 20 revisions as <code class="literal">cat-file.c</code>, was renamed to <code class="literal">builtin/cat-file.c</code>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1903 when made a builtin, and then saw less than 10 versions).
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]1904</li></ul></div><p>So, look into <code class="literal">builtin/cat-file.c</code>, search for <code class="literal">cmd_cat_file()</code> and look what
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1905it does.</p><pre class="literallayout"> git_config(git_default_config);
1906 if (argc != 3)
1907 usage("git cat-file [-t|-s|-e|-p|&lt;type&gt;] &lt;sha1&gt;");
1908 if (get_sha1(argv[2], sha1))
1909 die("Not a valid object name %s", argv[2]);</pre><p>Let’s skip over the obvious details; the only really interesting part
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1910here is the call to <code class="literal">get_sha1()</code>. It tries to interpret <code class="literal">argv[2]</code> as an
1911object name, and if it refers to an object which is present in the current
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1912repository, it writes the resulting SHA-1 into the variable <code class="literal">sha1</code>.</p><p>Two things are interesting here:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1913<code class="literal">get_sha1()</code> returns 0 on <span class="emphasis"><em>success</em></span>. This might surprise some new
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1914 Git hackers, but there is a long tradition in UNIX to return different
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1915 negative numbers in case of different errors—and 0 on success.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1916</li><li class="listitem">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1917the variable <code class="literal">sha1</code> in the function signature of <code class="literal">get_sha1()</code> is <code class="literal">unsigned
1918 char *</code>, but is actually expected to be a pointer to <code class="literal">unsigned
1919 char[20]</code>. This variable will contain the 160-bit SHA-1 of the given
1920 commit. Note that whenever a SHA-1 is passed as <code class="literal">unsigned char *</code>, it
1921 is the binary representation, as opposed to the ASCII representation in
1922 hex characters, which is passed as <code class="literal">char *</code>.
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1923</li></ul></div><p>You will see both of these things throughout the code.</p><p>Now, for the meat:</p><pre class="literallayout"> case 0:
1924 buf = read_object_with_reference(sha1, argv[1], &amp;size, NULL);</pre><p>This is how you read a blob (actually, not only a blob, but any type of
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1925object). To know how the function <code class="literal">read_object_with_reference()</code> actually
1926works, find the source code for it (something like <code class="literal">git grep
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1927read_object_with | grep ":[a-z]"</code> in the Git repository), and read
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1928the source.</p><p>To find out how the result can be used, just read on in <code class="literal">cmd_cat_file()</code>:</p><pre class="literallayout"> write_or_die(1, buf, size);</pre><p>Sometimes, you do not know where to look for a feature. In many such cases,
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1929it helps to search through the output of <code class="literal">git log</code>, and then <code class="literal">git show</code> the
1930corresponding commit.</p><p>Example: If you know that there was some test case for <code class="literal">git bundle</code>, but
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]1931do not remember where it was (yes, you <span class="emphasis"><em>could</em></span> <code class="literal">git grep bundle t/</code>, but that
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1932does not illustrate the point!):</p><pre class="literallayout">$ git log --no-merges t/</pre><p>In the pager (<code class="literal">less</code>), just search for "bundle", go a few lines back,
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1933and see that it is in commit 18449ab0… Now just copy this object name,
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]1934and paste it into the command line</p><pre class="literallayout">$ git show 18449ab0</pre><p>Voila.</p><p>Another example: Find out what to do in order to make some script a
Junio C Hamano3a3357e2013-06-26 23:20:56[diff] [blame]1935builtin:</p><pre class="literallayout">$ git log --no-merges --diff-filter=A builtin/*.c</pre><p>You see, Git is actually the best tool to find out about the source of Git
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]1936itself!</p></div></div><div class="chapter" title="Chapter 11. Git Glossary"><div class="titlepage"><div><div><h2 class="title"><a name="glossary"></a>Chapter 11. Git Glossary</h2></div></div></div><div class="variablelist"><dl><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1937<a name="def_alternate_object_database"></a>alternate object database
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1938</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1939 Via the alternates mechanism, a <a class="link" href="#def_repository">repository</a>
1940 can inherit part of its <a class="link" href="#def_object_database">object database</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1941 from another object database, which is called "alternate".
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1942</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1943<a name="def_bare_repository"></a>bare repository
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1944</span></dt><dd>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1945 A bare repository is normally an appropriately
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1946 named <a class="link" href="#def_directory">directory</a> with a <code class="literal">.git</code> suffix that does not
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1947 have a locally checked-out copy of any of the files under
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1948 revision control. That is, all of the Git
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1949 administrative and control files that would normally be present in the
1950 hidden <code class="literal">.git</code> sub-directory are directly present in the
1951 <code class="literal">repository.git</code> directory instead,
1952 and no other files are present and checked out. Usually publishers of
1953 public repositories make bare repositories available.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1954</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1955<a name="def_blob_object"></a>blob object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1956</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1957 Untyped <a class="link" href="#def_object">object</a>, e.g. the contents of a file.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1958</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1959<a name="def_branch"></a>branch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1960</span></dt><dd>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1961 A "branch" is an active line of development. The most recent
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1962 <a class="link" href="#def_commit">commit</a> on a branch is referred to as the tip of
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1963 that branch. The tip of the branch is referenced by a branch
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1964 <a class="link" href="#def_head">head</a>, which moves forward as additional development
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1965 is done on the branch. A single Git
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1966 <a class="link" href="#def_repository">repository</a> can track an arbitrary number of
1967 branches, but your <a class="link" href="#def_working_tree">working tree</a> is
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1968 associated with just one of them (the "current" or "checked out"
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1969 branch), and <a class="link" href="#def_HEAD">HEAD</a> points to that branch.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1970</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1971<a name="def_cache"></a>cache
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1972</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1973 Obsolete for: <a class="link" href="#def_index">index</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1974</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1975<a name="def_chain"></a>chain
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1976</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1977 A list of objects, where each <a class="link" href="#def_object">object</a> in the list contains
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1978 a reference to its successor (for example, the successor of a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1979 <a class="link" href="#def_commit">commit</a> could be one of its <a class="link" href="#def_parent">parents</a>).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1980</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1981<a name="def_changeset"></a>changeset
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1982</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1983 BitKeeper/cvsps speak for "<a class="link" href="#def_commit">commit</a>". Since Git does not
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1984 store changes, but states, it really does not make sense to use the term
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]1985 "changesets" with Git.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1986</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1987<a name="def_checkout"></a>checkout
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1988</span></dt><dd>
Junio C Hamanoa14a4032008-03-25 09:11:02[diff] [blame]1989 The action of updating all or part of the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1990 <a class="link" href="#def_working_tree">working tree</a> with a <a class="link" href="#def_tree_object">tree object</a>
1991 or <a class="link" href="#def_blob_object">blob</a> from the
1992 <a class="link" href="#def_object_database">object database</a>, and updating the
1993 <a class="link" href="#def_index">index</a> and <a class="link" href="#def_HEAD">HEAD</a> if the whole working tree has
1994 been pointed at a new <a class="link" href="#def_branch">branch</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1995</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1996<a name="def_cherry-picking"></a>cherry-picking
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1997</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1998 In <a class="link" href="#def_SCM">SCM</a> jargon, "cherry pick" means to choose a subset of
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1999 changes out of a series of changes (typically commits) and record them
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2000 as a new series of changes on top of a different codebase. In Git, this is
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]2001 performed by the "git cherry-pick" command to extract the change introduced
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2002 by an existing <a class="link" href="#def_commit">commit</a> and to record it based on the tip
2003 of the current <a class="link" href="#def_branch">branch</a> as a new commit.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2004</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2005<a name="def_clean"></a>clean
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2006</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2007 A <a class="link" href="#def_working_tree">working tree</a> is clean, if it
2008 corresponds to the <a class="link" href="#def_revision">revision</a> referenced by the current
2009 <a class="link" href="#def_head">head</a>. Also see "<a class="link" href="#def_dirty">dirty</a>".
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2010</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2011<a name="def_commit"></a>commit
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2012</span></dt><dd><p class="simpara">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2013 As a noun: A single point in the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2014 Git history; the entire history of a project is represented as a
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2015 set of interrelated commits. The word "commit" is often
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2016 used by Git in the same places other revision control systems
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2017 use the words "revision" or "version". Also used as a short
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2018 hand for <a class="link" href="#def_commit_object">commit object</a>.
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2019</p><p class="simpara">As a verb: The action of storing a new snapshot of the project’s
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2020state in the Git history, by creating a new commit representing the current
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2021state of the <a class="link" href="#def_index">index</a> and advancing <a class="link" href="#def_HEAD">HEAD</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2022to point at the new commit.</p></dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2023<a name="def_commit_object"></a>commit object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2024</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2025 An <a class="link" href="#def_object">object</a> which contains the information about a
2026 particular <a class="link" href="#def_revision">revision</a>, such as <a class="link" href="#def_parent">parents</a>, committer,
2027 author, date and the <a class="link" href="#def_tree_object">tree object</a> which corresponds
2028 to the top <a class="link" href="#def_directory">directory</a> of the stored
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2029 revision.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2030</dd><dt><span class="term">
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]2031<a name="def_commit-ish"></a>commit-ish (also committish)
2032</span></dt><dd>
2033 A <a class="link" href="#def_commit_object">commit object</a> or an
2034 <a class="link" href="#def_object">object</a> that can be recursively dereferenced to
2035 a commit object.
2036 The following are all commit-ishes:
2037 a commit object,
2038 a <a class="link" href="#def_tag_object">tag object</a> that points to a commit
2039 object,
2040 a tag object that points to a tag object that points to a
2041 commit object,
2042 etc.
2043</dd><dt><span class="term">
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2044<a name="def_core_git"></a>core Git
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2045</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2046 Fundamental data structures and utilities of Git. Exposes only limited
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2047 source code management tools.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2048</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2049<a name="def_DAG"></a>DAG
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2050</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2051 Directed acyclic graph. The <a class="link" href="#def_commit_object">commit objects</a> form a
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2052 directed acyclic graph, because they have parents (directed), and the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2053 graph of commit objects is acyclic (there is no <a class="link" href="#def_chain">chain</a>
2054 which begins and ends with the same <a class="link" href="#def_object">object</a>).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2055</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2056<a name="def_dangling_object"></a>dangling object
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2057</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2058 An <a class="link" href="#def_unreachable_object">unreachable object</a> which is not
2059 <a class="link" href="#def_reachable">reachable</a> even from other unreachable objects; a
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2060 dangling object has no references to it from any
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2061 reference or <a class="link" href="#def_object">object</a> in the <a class="link" href="#def_repository">repository</a>.
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2062</dd><dt><span class="term">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2063<a name="def_detached_HEAD"></a>detached HEAD
Junio C Hamanoea3b7522013-04-18 19:37:53[diff] [blame]2064</span></dt><dd><p class="simpara">
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2065 Normally the <a class="link" href="#def_HEAD">HEAD</a> stores the name of a
Junio C Hamanoea3b7522013-04-18 19:37:53[diff] [blame]2066 <a class="link" href="#def_branch">branch</a>, and commands that operate on the
2067 history HEAD represents operate on the history leading to the
2068 tip of the branch the HEAD points at. However, Git also
2069 allows you to <a class="link" href="#def_checkout">check out</a> an arbitrary
2070 <a class="link" href="#def_commit">commit</a> that isn’t necessarily the tip of any
2071 particular branch. The HEAD in such a state is called
2072 "detached".
2073</p><p class="simpara">Note that commands that operate on the history of the current branch
2074(e.g. <code class="literal">git commit</code> to build a new history on top of it) still work
2075while the HEAD is detached. They update the HEAD to point at the tip
2076of the updated history without affecting any branch. Commands that
2077update or inquire information <span class="emphasis"><em>about</em></span> the current branch (e.g. <code class="literal">git
Junio C Hamano8401f142013-07-12 22:47:46[diff] [blame]2078branch --set-upstream-to</code> that sets what remote-tracking branch the
Junio C Hamanoea3b7522013-04-18 19:37:53[diff] [blame]2079current branch integrates with) obviously do not work, as there is no
2080(real) current branch to ask about in this state.</p></dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2081<a name="def_directory"></a>directory
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2082</span></dt><dd>
2083 The list you get with "ls" :-)
2084</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2085<a name="def_dirty"></a>dirty
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2086</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2087 A <a class="link" href="#def_working_tree">working tree</a> is said to be "dirty" if
2088 it contains modifications which have not been <a class="link" href="#def_commit">committed</a> to the current
2089 <a class="link" href="#def_branch">branch</a>.
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2090</dd><dt><span class="term">
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2091<a name="def_evil_merge"></a>evil merge
2092</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2093 An evil merge is a <a class="link" href="#def_merge">merge</a> that introduces changes that
2094 do not appear in any <a class="link" href="#def_parent">parent</a>.
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2095</dd><dt><span class="term">
Junio C Hamano3f680f32009-11-16 02:10:54[diff] [blame]2096<a name="def_fast_forward"></a>fast-forward
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2097</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2098 A fast-forward is a special type of <a class="link" href="#def_merge">merge</a> where you have a
2099 <a class="link" href="#def_revision">revision</a> and you are "merging" another
2100 <a class="link" href="#def_branch">branch</a>'s changes that happen to be a descendant of what
2101 you have. In such these cases, you do not make a new <a class="link" href="#def_merge">merge</a>
2102 <a class="link" href="#def_commit">commit</a> but instead just update to his
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2103 revision. This will happen frequently on a
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]2104 <a class="link" href="#def_remote_tracking_branch">remote-tracking branch</a> of a remote
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2105 <a class="link" href="#def_repository">repository</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2106</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2107<a name="def_fetch"></a>fetch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2108</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2109 Fetching a <a class="link" href="#def_branch">branch</a> means to get the
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2110 branch’s <a class="link" href="#def_head_ref">head ref</a> from a remote
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2111 <a class="link" href="#def_repository">repository</a>, to find out which objects are
2112 missing from the local <a class="link" href="#def_object_database">object database</a>,
2113 and to get them, too. See also <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2114</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2115<a name="def_file_system"></a>file system
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2116</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2117 Linus Torvalds originally designed Git to be a user space file system,
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2118 i.e. the infrastructure to hold files and directories. That ensured the
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2119 efficiency and speed of Git.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2120</dd><dt><span class="term">
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2121<a name="def_git_archive"></a>Git archive
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2122</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2123 Synonym for <a class="link" href="#def_repository">repository</a> (for arch people).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2124</dd><dt><span class="term">
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2125<a name="def_gitfile"></a>gitfile
2126</span></dt><dd>
2127 A plain file <code class="literal">.git</code> at the root of a working tree that
2128 points at the directory that is the real repository.
2129</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2130<a name="def_grafts"></a>grafts
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2131</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2132 Grafts enables two otherwise different lines of development to be joined
2133 together by recording fake ancestry information for commits. This way
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2134 you can make Git pretend the set of <a class="link" href="#def_parent">parents</a> a <a class="link" href="#def_commit">commit</a> has
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2135 is different from what was recorded when the commit was
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2136 created. Configured via the <code class="literal">.git/info/grafts</code> file.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2137</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2138<a name="def_hash"></a>hash
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2139</span></dt><dd>
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2140 In Git’s context, synonym for <a class="link" href="#def_object_name">object name</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2141</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2142<a name="def_head"></a>head
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2143</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2144 A <a class="link" href="#def_ref">named reference</a> to the <a class="link" href="#def_commit">commit</a> at the tip of a
Junio C Hamano360e3a12011-07-13 23:51:56[diff] [blame]2145 <a class="link" href="#def_branch">branch</a>. Heads are stored in a file in
2146 <code class="literal">$GIT_DIR/refs/heads/</code> directory, except when using packed refs. (See
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2147 <a class="ulink" href="git-pack-refs.html" target="_top">git-pack-refs(1)</a>.)
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2148</dd><dt><span class="term">
2149<a name="def_HEAD"></a>HEAD
2150</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2151 The current <a class="link" href="#def_branch">branch</a>. In more detail: Your <a class="link" href="#def_working_tree">working tree</a> is normally derived from the state of the tree
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2152 referred to by HEAD. HEAD is a reference to one of the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2153 <a class="link" href="#def_head">heads</a> in your repository, except when using a
Junio C Hamano360e3a12011-07-13 23:51:56[diff] [blame]2154 <a class="link" href="#def_detached_HEAD">detached HEAD</a>, in which case it directly
2155 references an arbitrary commit.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2156</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2157<a name="def_head_ref"></a>head ref
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2158</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2159 A synonym for <a class="link" href="#def_head">head</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2160</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2161<a name="def_hook"></a>hook
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2162</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2163 During the normal execution of several Git commands, call-outs are made
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2164 to optional scripts that allow a developer to add functionality or
2165 checking. Typically, the hooks allow for a command to be pre-verified
2166 and potentially aborted, and allow for a post-notification after the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2167 operation is done. The hook scripts are found in the
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2168 <code class="literal">$GIT_DIR/hooks/</code> directory, and are enabled by simply
Junio C Hamano116db352008-12-17 19:48:40[diff] [blame]2169 removing the <code class="literal">.sample</code> suffix from the filename. In earlier versions
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2170 of Git you had to make them executable.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2171</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2172<a name="def_index"></a>index
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2173</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2174 A collection of files with stat information, whose contents are stored
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2175 as objects. The index is a stored version of your
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2176 <a class="link" href="#def_working_tree">working tree</a>. Truth be told, it can also contain a second, and even
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2177 a third version of a working tree, which are used
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2178 when <a class="link" href="#def_merge">merging</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2179</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2180<a name="def_index_entry"></a>index entry
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2181</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2182 The information regarding a particular file, stored in the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2183 <a class="link" href="#def_index">index</a>. An index entry can be unmerged, if a
2184 <a class="link" href="#def_merge">merge</a> was started, but not yet finished (i.e. if
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2185 the index contains multiple versions of that file).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2186</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2187<a name="def_master"></a>master
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2188</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2189 The default development <a class="link" href="#def_branch">branch</a>. Whenever you
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2190 create a Git <a class="link" href="#def_repository">repository</a>, a branch named
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2191 "master" is created, and becomes the active branch. In most
2192 cases, this contains the local development, though that is
2193 purely by convention and is not required.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2194</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2195<a name="def_merge"></a>merge
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2196</span></dt><dd><p class="simpara">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2197 As a verb: To bring the contents of another
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2198 <a class="link" href="#def_branch">branch</a> (possibly from an external
2199 <a class="link" href="#def_repository">repository</a>) into the current branch. In the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2200 case where the merged-in branch is from a different repository,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2201 this is done by first <a class="link" href="#def_fetch">fetching</a> the remote branch
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2202 and then merging the result into the current branch. This
2203 combination of fetch and merge operations is called a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2204 <a class="link" href="#def_pull">pull</a>. Merging is performed by an automatic process
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2205 that identifies changes made since the branches diverged, and
2206 then applies all those changes together. In cases where changes
2207 conflict, manual intervention may be required to complete the
2208 merge.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2209</p><p class="simpara">As a noun: unless it is a <a class="link" href="#def_fast_forward">fast-forward</a>, a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2210successful merge results in the creation of a new <a class="link" href="#def_commit">commit</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2211representing the result of the merge, and having as
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2212<a class="link" href="#def_parent">parents</a> the tips of the merged <a class="link" href="#def_branch">branches</a>.
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2213This commit is referred to as a "merge commit", or sometimes just a
2214"merge".</p></dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2215<a name="def_object"></a>object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2216</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2217 The unit of storage in Git. It is uniquely identified by the
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2218 <a class="link" href="#def_SHA1">SHA-1</a> of its contents. Consequently, an
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2219 object can not be changed.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2220</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2221<a name="def_object_database"></a>object database
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2222</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2223 Stores a set of "objects", and an individual <a class="link" href="#def_object">object</a> is
2224 identified by its <a class="link" href="#def_object_name">object name</a>. The objects usually
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2225 live in <code class="literal">$GIT_DIR/objects/</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2226</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2227<a name="def_object_identifier"></a>object identifier
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2228</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2229 Synonym for <a class="link" href="#def_object_name">object name</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2230</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2231<a name="def_object_name"></a>object name
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2232</span></dt><dd>
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2233 The unique identifier of an <a class="link" href="#def_object">object</a>. The
2234 object name is usually represented by a 40 character
2235 hexadecimal string. Also colloquially called <a class="link" href="#def_SHA1">SHA-1</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2236</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2237<a name="def_object_type"></a>object type
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2238</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2239 One of the identifiers "<a class="link" href="#def_commit_object">commit</a>",
2240 "<a class="link" href="#def_tree_object">tree</a>", "<a class="link" href="#def_tag_object">tag</a>" or
2241 "<a class="link" href="#def_blob_object">blob</a>" describing the type of an
2242 <a class="link" href="#def_object">object</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2243</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2244<a name="def_octopus"></a>octopus
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2245</span></dt><dd>
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2246 To <a class="link" href="#def_merge">merge</a> more than two <a class="link" href="#def_branch">branches</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2247</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2248<a name="def_origin"></a>origin
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2249</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2250 The default upstream <a class="link" href="#def_repository">repository</a>. Most projects have
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2251 at least one upstream project which they track. By default
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2252 <span class="emphasis"><em>origin</em></span> is used for that purpose. New upstream updates
Junio C Hamano8401f142013-07-12 22:47:46[diff] [blame]2253 will be fetched into <a class="link" href="#def_remote_tracking_branch">remote-tracking branches</a> named
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2254 origin/name-of-upstream-branch, which you can see using
Junio C Hamanoea82cff2009-03-18 01:54:48[diff] [blame]2255 <code class="literal">git branch -r</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2256</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2257<a name="def_pack"></a>pack
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2258</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2259 A set of objects which have been compressed into one file (to save space
2260 or to transmit them efficiently).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2261</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2262<a name="def_pack_index"></a>pack index
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2263</span></dt><dd>
2264 The list of identifiers, and other information, of the objects in a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2265 <a class="link" href="#def_pack">pack</a>, to assist in efficiently accessing the contents of a
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2266 pack.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2267</dd><dt><span class="term">
Junio C Hamano63c2bc92011-02-28 06:41:28[diff] [blame]2268<a name="def_pathspec"></a>pathspec
2269</span></dt><dd><p class="simpara">
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2270 Pattern used to limit paths in Git commands.
Junio C Hamano63c2bc92011-02-28 06:41:28[diff] [blame]2271</p><p class="simpara">Pathspecs are used on the command line of "git ls-files", "git
Junio C Hamano2a294cd2011-05-23 23:06:31[diff] [blame]2272ls-tree", "git add", "git grep", "git diff", "git checkout",
2273and many other commands to
Junio C Hamano63c2bc92011-02-28 06:41:28[diff] [blame]2274limit the scope of operations to some subset of the tree or
2275worktree. See the documentation of each command for whether
2276paths are relative to the current directory or toplevel. The
2277pathspec syntax is as follows:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
2278any path matches itself
2279</li><li class="listitem">
2280the pathspec up to the last slash represents a
2281 directory prefix. The scope of that pathspec is
2282 limited to that subtree.
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2283</li><li class="listitem">
Junio C Hamano63c2bc92011-02-28 06:41:28[diff] [blame]2284the rest of the pathspec is a pattern for the remainder
2285 of the pathname. Paths relative to the directory
2286 prefix will be matched against that pattern using fnmatch(3);
2287 in particular, <span class="emphasis"><em>*</em></span> and <span class="emphasis"><em>?</em></span> <span class="emphasis"><em>can</em></span> match directory separators.
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2288</li></ul></div><p class="simpara">For example, Documentation/*.jpg will match all .jpg files
Junio C Hamano63c2bc92011-02-28 06:41:28[diff] [blame]2289in the Documentation subtree,
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2290including Documentation/chapter_1/figure_1.jpg.</p><p class="simpara">A pathspec that begins with a colon <code class="literal">:</code> has special meaning. In the
Junio C Hamano2a294cd2011-05-23 23:06:31[diff] [blame]2291short form, the leading colon <code class="literal">:</code> is followed by zero or more "magic
2292signature" letters (which optionally is terminated by another colon <code class="literal">:</code>),
2293and the remainder is the pattern to match against the path. The optional
2294colon that terminates the "magic signature" can be omitted if the pattern
2295begins with a character that cannot be a "magic signature" and is not a
2296colon.</p><p class="simpara">In the long form, the leading colon <code class="literal">:</code> is followed by a open
2297parenthesis <code class="literal">(</code>, a comma-separated list of zero or more "magic words",
2298and a close parentheses <code class="literal">)</code>, and the remainder is the pattern to match
2299against the path.</p><p class="simpara">The "magic signature" consists of an ASCII symbol that is not
Junio C Hamano8eac2682013-09-09 22:35:20[diff] [blame]2300alphanumeric.</p><div class="variablelist"><dl><dt><span class="term">
2301top <code class="literal">/</code>
2302</span></dt><dd>
2303 The magic word <code class="literal">top</code> (mnemonic: <code class="literal">/</code>) makes the pattern match
2304 from the root of the working tree, even when you are running
2305 the command from inside a subdirectory.
2306</dd><dt><span class="term">
2307literal
2308</span></dt><dd>
2309 Wildcards in the pattern such as <code class="literal">*</code> or <code class="literal">?</code> are treated
2310 as literal characters.
2311</dd><dt><span class="term">
2312icase
2313</span></dt><dd>
2314 Case insensitive match.
2315</dd><dt><span class="term">
2316glob
2317</span></dt><dd><p class="simpara">
2318 Git treats the pattern as a shell glob suitable for
2319 consumption by fnmatch(3) with the FNM_PATHNAME flag:
2320 wildcards in the pattern will not match a / in the pathname.
2321 For example, "Documentation/*.html" matches
2322 "Documentation/git.html" but not "Documentation/ppc/ppc.html"
2323 or "tools/perf/Documentation/perf.html".
2324</p><p class="simpara">Two consecutive asterisks ("<code class="literal">**</code>") in patterns matched against
2325full pathname may have special meaning:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
2326A leading "<code class="literal">**</code>" followed by a slash means match in all
2327 directories. For example, "<code class="literal">**/foo</code>" matches file or directory
2328 "<code class="literal">foo</code>" anywhere, the same as pattern "<code class="literal">foo</code>". "**/foo/bar"
2329 matches file or directory "<code class="literal">bar</code>" anywhere that is directly
2330 under directory "<code class="literal">foo</code>".
2331</li><li class="listitem">
2332A trailing "/<span class="strong"><strong>" matches everything inside. For example,
2333 "abc/</strong></span>" matches all files inside directory "abc", relative
2334 to the location of the <code class="literal">.gitignore</code> file, with infinite depth.
2335</li><li class="listitem">
2336A slash followed by two consecutive asterisks then a slash
2337 matches zero or more directories. For example, "<code class="literal">a/**/b</code>"
2338 matches "<code class="literal">a/b</code>", "<code class="literal">a/x/b</code>", "<code class="literal">a/x/y/b</code>" and so on.
2339</li><li class="listitem"><p class="simpara">
2340Other consecutive asterisks are considered invalid.
2341</p><p class="simpara">Glob magic is incompatible with literal magic.</p></li></ul></div></dd></dl></div><p class="simpara">Currently only the slash <code class="literal">/</code> is recognized as the "magic signature",
2342but it is envisioned that we will support more types of magic in later
2343versions of Git.</p><p class="simpara">A pathspec with only a colon means "there is no pathspec". This form
Junio C Hamano2a294cd2011-05-23 23:06:31[diff] [blame]2344should not be combined with other pathspec.</p></dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2345<a name="def_parent"></a>parent
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2346</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2347 A <a class="link" href="#def_commit_object">commit object</a> contains a (possibly empty) list
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2348 of the logical predecessor(s) in the line of development, i.e. its
2349 parents.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2350</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2351<a name="def_pickaxe"></a>pickaxe
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2352</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2353 The term <a class="link" href="#def_pickaxe">pickaxe</a> refers to an option to the diffcore
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2354 routines that help select changes that add or delete a given text
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2355 string. With the <code class="literal">--pickaxe-all</code> option, it can be used to view the full
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2356 <a class="link" href="#def_changeset">changeset</a> that introduced or removed, say, a
2357 particular line of text. See <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2358</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2359<a name="def_plumbing"></a>plumbing
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2360</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2361 Cute name for <a class="link" href="#def_core_git">core Git</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2362</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2363<a name="def_porcelain"></a>porcelain
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2364</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2365 Cute name for programs and program suites depending on
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2366 <a class="link" href="#def_core_git">core Git</a>, presenting a high level access to
2367 core Git. Porcelains expose more of a <a class="link" href="#def_SCM">SCM</a>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2368 interface than the <a class="link" href="#def_plumbing">plumbing</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2369</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2370<a name="def_pull"></a>pull
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2371</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2372 Pulling a <a class="link" href="#def_branch">branch</a> means to <a class="link" href="#def_fetch">fetch</a> it and
2373 <a class="link" href="#def_merge">merge</a> it. See also <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2374</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2375<a name="def_push"></a>push
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2376</span></dt><dd>
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2377 Pushing a <a class="link" href="#def_branch">branch</a> means to get the branch’s
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2378 <a class="link" href="#def_head_ref">head ref</a> from a remote <a class="link" href="#def_repository">repository</a>,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2379 find out if it is a direct ancestor to the branch’s local
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]2380 head ref, and in that case, putting all
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2381 objects, which are <a class="link" href="#def_reachable">reachable</a> from the local
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2382 head ref, and which are missing from the remote
2383 repository, into the remote
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2384 <a class="link" href="#def_object_database">object database</a>, and updating the remote
2385 head ref. If the remote <a class="link" href="#def_head">head</a> is not an
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2386 ancestor to the local head, the push fails.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2387</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2388<a name="def_reachable"></a>reachable
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2389</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2390 All of the ancestors of a given <a class="link" href="#def_commit">commit</a> are said to be
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2391 "reachable" from that commit. More
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2392 generally, one <a class="link" href="#def_object">object</a> is reachable from
2393 another if we can reach the one from the other by a <a class="link" href="#def_chain">chain</a>
2394 that follows <a class="link" href="#def_tag">tags</a> to whatever they tag,
2395 <a class="link" href="#def_commit_object">commits</a> to their parents or trees, and
2396 <a class="link" href="#def_tree_object">trees</a> to the trees or <a class="link" href="#def_blob_object">blobs</a>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2397 that they contain.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2398</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2399<a name="def_rebase"></a>rebase
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2400</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2401 To reapply a series of changes from a <a class="link" href="#def_branch">branch</a> to a
2402 different base, and reset the <a class="link" href="#def_head">head</a> of that branch
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2403 to the result.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2404</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2405<a name="def_ref"></a>ref
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]2406</span></dt><dd><p class="simpara">
2407 A name that begins with <code class="literal">refs/</code> (e.g. <code class="literal">refs/heads/master</code>)
2408 that points to an <a class="link" href="#def_object_name">object name</a> or another
2409 ref (the latter is called a <a class="link" href="#def_symref">symbolic ref</a>).
2410 For convenience, a ref can sometimes be abbreviated when used
2411 as an argument to a Git command; see <a class="ulink" href="gitrevisions.html" target="_top">gitrevisions(7)</a>
2412 for details.
2413 Refs are stored in the <a class="link" href="#def_repository">repository</a>.
2414</p><p class="simpara">The ref namespace is hierarchical.
2415Different subhierarchies are used for different purposes (e.g. the
2416<code class="literal">refs/heads/</code> hierarchy is used to represent local branches).</p><p class="simpara">There are a few special-purpose refs that do not begin with <code class="literal">refs/</code>.
2417The most notable example is <code class="literal">HEAD</code>.</p></dd><dt><span class="term">
Junio C Hamanobb0f4042007-07-04 06:41:40[diff] [blame]2418<a name="def_reflog"></a>reflog
2419</span></dt><dd>
2420 A reflog shows the local "history" of a ref. In other words,
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2421 it can tell you what the 3rd last revision in <span class="emphasis"><em>this</em></span> repository
2422 was, and what was the current state in <span class="emphasis"><em>this</em></span> repository,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2423 yesterday 9:14pm. See <a class="ulink" href="git-reflog.html" target="_top">git-reflog(1)</a> for details.
Junio C Hamanobb0f4042007-07-04 06:41:40[diff] [blame]2424</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2425<a name="def_refspec"></a>refspec
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2426</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2427 A "refspec" is used by <a class="link" href="#def_fetch">fetch</a> and
2428 <a class="link" href="#def_push">push</a> to describe the mapping between remote
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2429 <a class="link" href="#def_ref">ref</a> and local ref.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2430</dd><dt><span class="term">
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]2431<a name="def_remote_tracking_branch"></a>remote-tracking branch
2432</span></dt><dd>
Junio C Hamanoc7102962013-05-29 23:57:17[diff] [blame]2433 A <a class="link" href="#def_ref">ref</a> that is used to follow changes from another
2434 <a class="link" href="#def_repository">repository</a>. It typically looks like
2435 <span class="emphasis"><em>refs/remotes/foo/bar</em></span> (indicating that it tracks a branch named
2436 <span class="emphasis"><em>bar</em></span> in a remote named <span class="emphasis"><em>foo</em></span>), and matches the right-hand-side of
2437 a configured fetch <a class="link" href="#def_refspec">refspec</a>. A remote-tracking
2438 branch should not contain direct modifications or have local
2439 commits made to it.
Junio C Hamano97bcb482010-11-25 03:16:07[diff] [blame]2440</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2441<a name="def_repository"></a>repository
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2442</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2443 A collection of <a class="link" href="#def_ref">refs</a> together with an
2444 <a class="link" href="#def_object_database">object database</a> containing all objects
2445 which are <a class="link" href="#def_reachable">reachable</a> from the refs, possibly
2446 accompanied by meta data from one or more <a class="link" href="#def_porcelain">porcelains</a>. A
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2447 repository can share an object database with other repositories
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2448 via <a class="link" href="#def_alternate_object_database">alternates mechanism</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2449</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2450<a name="def_resolve"></a>resolve
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2451</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2452 The action of fixing up manually what a failed automatic
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2453 <a class="link" href="#def_merge">merge</a> left behind.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2454</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2455<a name="def_revision"></a>revision
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2456</span></dt><dd>
Junio C Hamanof26c77e2013-04-27 00:06:04[diff] [blame]2457 Synonym for <a class="link" href="#def_commit">commit</a> (the noun).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2458</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2459<a name="def_rewind"></a>rewind
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2460</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2461 To throw away part of the development, i.e. to assign the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2462 <a class="link" href="#def_head">head</a> to an earlier <a class="link" href="#def_revision">revision</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2463</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2464<a name="def_SCM"></a>SCM
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2465</span></dt><dd>
2466 Source code management (tool).
2467</dd><dt><span class="term">
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2468<a name="def_SHA1"></a>SHA-1
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2469</span></dt><dd>
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2470 "Secure Hash Algorithm 1"; a cryptographic hash function.
2471 In the context of Git used as a synonym for <a class="link" href="#def_object_name">object name</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2472</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2473<a name="def_shallow_repository"></a>shallow repository
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2474</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2475 A shallow <a class="link" href="#def_repository">repository</a> has an incomplete
2476 history some of whose <a class="link" href="#def_commit">commits</a> have <a class="link" href="#def_parent">parents</a> cauterized away (in other
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2477 words, Git is told to pretend that these commits do not have the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2478 parents, even though they are recorded in the <a class="link" href="#def_commit_object">commit object</a>). This is sometimes useful when you are interested only in the
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2479 recent history of a project even though the real history recorded in the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2480 upstream is much larger. A shallow repository
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2481 is created by giving the <code class="literal">--depth</code> option to <a class="ulink" href="git-clone.html" target="_top">git-clone(1)</a>, and
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2482 its history can be later deepened with <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2483</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2484<a name="def_symref"></a>symref
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2485</span></dt><dd>
Junio C Hamanoe3f080d2013-04-22 02:27:13[diff] [blame]2486 Symbolic reference: instead of containing the <a class="link" href="#def_SHA1">SHA-1</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2487 id itself, it is of the format <span class="emphasis"><em>ref: refs/some/thing</em></span> and when
2488 referenced, it recursively dereferences to this reference.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2489 <span class="emphasis"><em><a class="link" href="#def_HEAD">HEAD</a></em></span> is a prime example of a symref. Symbolic
2490 references are manipulated with the <a class="ulink" href="git-symbolic-ref.html" target="_top">git-symbolic-ref(1)</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2491 command.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2492</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2493<a name="def_tag"></a>tag
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2494</span></dt><dd>
Junio C Hamano360e3a12011-07-13 23:51:56[diff] [blame]2495 A <a class="link" href="#def_ref">ref</a> under <code class="literal">refs/tags/</code> namespace that points to an
2496 object of an arbitrary type (typically a tag points to either a
2497 <a class="link" href="#def_tag_object">tag</a> or a <a class="link" href="#def_commit_object">commit object</a>).
2498 In contrast to a <a class="link" href="#def_head">head</a>, a tag is not updated by
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2499 the <code class="literal">commit</code> command. A Git tag has nothing to do with a Lisp
Junio C Hamano360e3a12011-07-13 23:51:56[diff] [blame]2500 tag (which would be called an <a class="link" href="#def_object_type">object type</a>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2501 in Git’s context). A tag is most typically used to mark a particular
Junio C Hamano360e3a12011-07-13 23:51:56[diff] [blame]2502 point in the commit ancestry <a class="link" href="#def_chain">chain</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2503</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2504<a name="def_tag_object"></a>tag object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2505</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2506 An <a class="link" href="#def_object">object</a> containing a <a class="link" href="#def_ref">ref</a> pointing to
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2507 another object, which can contain a message just like a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2508 <a class="link" href="#def_commit_object">commit object</a>. It can also contain a (PGP)
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2509 signature, in which case it is called a "signed tag object".
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2510</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2511<a name="def_topic_branch"></a>topic branch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2512</span></dt><dd>
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2513 A regular Git <a class="link" href="#def_branch">branch</a> that is used by a developer to
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2514 identify a conceptual line of development. Since branches are very easy
2515 and inexpensive, it is often desirable to have several small branches
2516 that each contain very well defined concepts or small incremental yet
2517 related changes.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2518</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2519<a name="def_tree"></a>tree
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2520</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2521 Either a <a class="link" href="#def_working_tree">working tree</a>, or a <a class="link" href="#def_tree_object">tree object</a> together with the dependent <a class="link" href="#def_blob_object">blob</a> and tree objects
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2522 (i.e. a stored representation of a working tree).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2523</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2524<a name="def_tree_object"></a>tree object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2525</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2526 An <a class="link" href="#def_object">object</a> containing a list of file names and modes along
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2527 with refs to the associated blob and/or tree objects. A
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2528 <a class="link" href="#def_tree">tree</a> is equivalent to a <a class="link" href="#def_directory">directory</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2529</dd><dt><span class="term">
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]2530<a name="def_tree-ish"></a>tree-ish (also treeish)
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2531</span></dt><dd>
Junio C Hamanoe6f28d02013-09-17 21:34:00[diff] [blame]2532 A <a class="link" href="#def_tree_object">tree object</a> or an <a class="link" href="#def_object">object</a>
2533 that can be recursively dereferenced to a tree object.
2534 Dereferencing a <a class="link" href="#def_commit_object">commit object</a> yields the
2535 tree object corresponding to the <a class="link" href="#def_revision">revision</a>'s
2536 top <a class="link" href="#def_directory">directory</a>.
2537 The following are all tree-ishes:
2538 a <a class="link" href="#def_commit-ish">commit-ish</a>,
2539 a tree object,
2540 a <a class="link" href="#def_tag_object">tag object</a> that points to a tree object,
2541 a tag object that points to a tag object that points to a tree
2542 object,
2543 etc.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2544</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2545<a name="def_unmerged_index"></a>unmerged index
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2546</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2547 An <a class="link" href="#def_index">index</a> which contains unmerged
2548 <a class="link" href="#def_index_entry">index entries</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2549</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2550<a name="def_unreachable_object"></a>unreachable object
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2551</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2552 An <a class="link" href="#def_object">object</a> which is not <a class="link" href="#def_reachable">reachable</a> from a
2553 <a class="link" href="#def_branch">branch</a>, <a class="link" href="#def_tag">tag</a>, or any other reference.
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2554</dd><dt><span class="term">
Junio C Hamano98e32c32009-04-13 02:39:53[diff] [blame]2555<a name="def_upstream_branch"></a>upstream branch
2556</span></dt><dd>
2557 The default <a class="link" href="#def_branch">branch</a> that is merged into the branch in
2558 question (or the branch in question is rebased onto). It is configured
2559 via branch.&lt;name&gt;.remote and branch.&lt;name&gt;.merge. If the upstream branch
2560 of <span class="emphasis"><em>A</em></span> is <span class="emphasis"><em>origin/B</em></span> sometimes we say "<span class="emphasis"><em>A</em></span> is tracking <span class="emphasis"><em>origin/B</em></span>".
2561</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2562<a name="def_working_tree"></a>working tree
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2563</span></dt><dd>
Junio C Hamanoc0e55e72009-10-10 00:56:29[diff] [blame]2564 The tree of actual checked out files. The working tree normally
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2565 contains the contents of the <a class="link" href="#def_HEAD">HEAD</a> commit’s tree,
Junio C Hamanoc0e55e72009-10-10 00:56:29[diff] [blame]2566 plus any local changes that you have made but not yet committed.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2567</dd></dl></div></div><div class="appendix" title="Appendix A. Git Quick Reference"><div class="titlepage"><div><div><h2 class="title"><a name="git-quick-start"></a>Appendix A. Git Quick Reference</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#quick-creating-a-new-repository">Creating a new repository</a></span></dt><dt><span class="section"><a href="#managing-branches">Managing branches</a></span></dt><dt><span class="section"><a href="#exploring-history">Exploring history</a></span></dt><dt><span class="section"><a href="#making-changes">Making changes</a></span></dt><dt><span class="section"><a href="#merging">Merging</a></span></dt><dt><span class="section"><a href="#sharing-your-changes">Sharing your changes</a></span></dt><dt><span class="section"><a href="#repository-maintenance">Repository maintenance</a></span></dt></dl></div><p>This is a quick summary of the major commands; the previous chapters
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]2568explain how these work in more detail.</p><div class="section" title="Creating a new repository"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="quick-creating-a-new-repository"></a>Creating a new repository</h2></div></div></div><p>From a tarball:</p><pre class="literallayout">$ tar xzf project.tar.gz
2569$ cd project
2570$ git init
2571Initialized empty Git repository in .git/
2572$ git add .
2573$ git commit</pre><p>From a remote repository:</p><pre class="literallayout">$ git clone git://example.com/pub/project.git
2574$ cd project</pre></div><div class="section" title="Managing branches"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="managing-branches"></a>Managing branches</h2></div></div></div><pre class="literallayout">$ git branch # list all local branches in this repo
2575$ git checkout test # switch working directory to branch "test"
2576$ git branch new # create branch "new" starting at current HEAD
2577$ git branch -d new # delete branch "new"</pre><p>Instead of basing a new branch on current HEAD (the default), use:</p><pre class="literallayout">$ git branch new test # branch named "test"
2578$ git branch new v2.6.15 # tag named v2.6.15
2579$ git branch new HEAD^ # commit before the most recent
2580$ git branch new HEAD^^ # commit before that
2581$ git branch new test~10 # ten commits before tip of branch "test"</pre><p>Create and switch to a new branch at the same time:</p><pre class="literallayout">$ git checkout -b new v2.6.15</pre><p>Update and examine branches from the repository you cloned from:</p><pre class="literallayout">$ git fetch # update
2582$ git branch -r # list
2583 origin/master
2584 origin/next
2585 ...
2586$ git checkout -b masterwork origin/master</pre><p>Fetch a branch from a different repository, and give it a new
2587name in your repository:</p><pre class="literallayout">$ git fetch git://example.com/project.git theirbranch:mybranch
2588$ git fetch git://example.com/project.git v2.6.15:mybranch</pre><p>Keep a list of repositories you work with regularly:</p><pre class="literallayout">$ git remote add example git://example.com/project.git
2589$ git remote # list remote repositories
2590example
2591origin
2592$ git remote show example # get details
2593* remote example
2594 URL: git://example.com/project.git
2595 Tracked remote branches
2596 master
2597 next
2598 ...
2599$ git fetch example # update branches from example
2600$ git branch -r # list all remote branches</pre></div><div class="section" title="Exploring history"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exploring-history"></a>Exploring history</h2></div></div></div><pre class="literallayout">$ gitk # visualize and browse history
2601$ git log # list all commits
2602$ git log src/ # ...modifying src/
2603$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
2604$ git log master..test # ...in branch test, not in branch master
2605$ git log test..master # ...in branch master, but not in test
2606$ git log test...master # ...in one branch, not in both
2607$ git log -S'foo()' # ...where difference contain "foo()"
2608$ git log --since="2 weeks ago"
2609$ git log -p # show patches as well
2610$ git show # most recent commit
2611$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
2612$ git diff v2.6.15..HEAD # diff with current head
2613$ git grep "foo()" # search working directory for "foo()"
2614$ git grep v2.6.15 "foo()" # search old tree for "foo()"
2615$ git show v2.6.15:a.txt # look at old version of a.txt</pre><p>Search for regressions:</p><pre class="literallayout">$ git bisect start
2616$ git bisect bad # current version is bad
2617$ git bisect good v2.6.13-rc2 # last known good revision
2618Bisecting: 675 revisions left to test after this
2619 # test here, then:
2620$ git bisect good # if this revision is good, or
2621$ git bisect bad # if this revision is bad.
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2622 # repeat until done.</pre></div><div class="section" title="Making changes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="making-changes"></a>Making changes</h2></div></div></div><p>Make sure Git knows who to blame:</p><pre class="literallayout">$ cat &gt;&gt;~/.gitconfig &lt;&lt;\EOF
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]2623[user]
2624 name = Your Name Comes Here
2625 email = you@yourdomain.example.com
2626EOF</pre><p>Select file contents to include in the next commit, then make the
2627commit:</p><pre class="literallayout">$ git add a.txt # updated file
2628$ git add b.txt # new file
2629$ git rm c.txt # old file
2630$ git commit</pre><p>Or, prepare and create the commit in one step:</p><pre class="literallayout">$ git commit d.txt # use latest content only of d.txt
2631$ git commit -a # use latest content of all tracked files</pre></div><div class="section" title="Merging"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging"></a>Merging</h2></div></div></div><pre class="literallayout">$ git merge test # merge branch "test" into the current branch
2632$ git pull git://example.com/project.git master
2633 # fetch and merge in remote branch
2634$ git pull . test # equivalent to git merge test</pre></div><div class="section" title="Sharing your changes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="sharing-your-changes"></a>Sharing your changes</h2></div></div></div><p>Importing or exporting patches:</p><pre class="literallayout">$ git format-patch origin..HEAD # format a patch for each commit
2635 # in HEAD but not in origin
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2636$ git am mbox # import patches from the mailbox "mbox"</pre><p>Fetch a branch in a different Git repository, then merge into the
Junio C Hamanoa00504d2012-08-27 21:11:23[diff] [blame]2637current branch:</p><pre class="literallayout">$ git pull git://example.com/project.git theirbranch</pre><p>Store the fetched branch into a local branch before merging into the
2638current branch:</p><pre class="literallayout">$ git pull git://example.com/project.git theirbranch:mybranch</pre><p>After creating commits on a local branch, update the remote
2639branch with your commits:</p><pre class="literallayout">$ git push ssh://example.com/project.git mybranch:theirbranch</pre><p>When remote and local branch are both named "test":</p><pre class="literallayout">$ git push ssh://example.com/project.git test</pre><p>Shortcut version for a frequently used remote repository:</p><pre class="literallayout">$ git remote add example ssh://example.com/project.git
2640$ git push example test</pre></div><div class="section" title="Repository maintenance"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="repository-maintenance"></a>Repository maintenance</h2></div></div></div><p>Check for corruption:</p><pre class="literallayout">$ git fsck</pre><p>Recompress, remove unused cruft:</p><pre class="literallayout">$ git gc</pre></div></div><div class="appendix" title="Appendix B. Notes and todo list for this manual"><div class="titlepage"><div><div><h2 class="title"><a name="todo"></a>Appendix B. Notes and todo list for this manual</h2></div></div></div><p>This is a work in progress.</p><p>The basic requirements:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2641It must be readable in order, from beginning to end, by someone
2642 intelligent with a basic grasp of the UNIX command line, but without
Junio C Hamano076ffcc2013-02-06 05:13:21[diff] [blame]2643 any special knowledge of Git. If necessary, any other prerequisites
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2644 should be specifically mentioned as they arise.
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2645</li><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2646Whenever possible, section headings should clearly describe the task
2647 they explain how to do, in language that requires no more knowledge
2648 than necessary: for example, "importing patches into a project" rather
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]2649 than "the <code class="literal">git am</code> command"
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2650</li></ul></div><p>Think about how to create a clear chapter dependency graph that will
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2651allow people to get to important topics without necessarily reading
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]2652everything in between.</p><p>Scan <code class="literal">Documentation/</code> for other stuff left out; in particular:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
Junio C Hamano68cf15a2010-11-06 01:01:59[diff] [blame]2653howto’s
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2654</li><li class="listitem">
Junio C Hamano947ab822013-03-19 23:07:29[diff] [blame]2655some of <code class="literal">technical/</code>?
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2656</li><li class="listitem">
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2657hooks
Junio C Hamano281025e2009-12-03 02:47:42[diff] [blame]2658</li><li class="listitem">
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2659list of commands in <a class="ulink" href="git.html" target="_top">git(1)</a>
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2660</li></ul></div><p>Scan email archives for other stuff left out</p><p>Scan man pages to see if any assume more background than this manual
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2661provides.</p><p>Simplify beginning by suggesting disconnected head instead of
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2662temporary branch creation?</p><p>Add more good examples. Entire sections of just cookbook examples
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2663might be a good idea; maybe make an "advanced examples" section a
2664standard end-of-chapter section?</p><p>Include cross-references to the glossary, where appropriate.</p><p>Document shallow clones? See draft 1.5.0 release notes for some
Junio C Hamanoee1e4282007-02-04 08:32:04[diff] [blame]2665documentation.</p><p>Add a section on working with other version control systems, including
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]2666CVS, Subversion, and just imports of series of release tarballs.</p><p>More details on gitweb?</p><p>Write a chapter on using plumbing and writing scripts.</p><p>Alternates, clone -reference, etc.</p><p>More on recovery from repository corruption. See:
Junio C Hamano58f587a2013-07-22 19:20:59[diff] [blame]2667 <a class="ulink" href="http://marc.info/?l=git&amp;m=117263864820799&amp;w=2" target="_top">http://marc.info/?l=git&amp;m=117263864820799&amp;w=2</a>
2668 <a class="ulink" href="http://marc.info/?l=git&amp;m=117147855503798&amp;w=2" target="_top">http://marc.info/?l=git&amp;m=117147855503798&amp;w=2</a></p></div></div></div></body></html>