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Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Git User's Manual (for version 1.5.3 or newer)</title><link rel="stylesheet" href="docbook-xsl.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.73.2"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a name="id316004"></a>Git User's Manual (for version 1.5.3 or newer)</h1></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="preface"><a href="#id394089">Preface</a></span></dt><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-comments-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="#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 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 -&gt; index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index -&gt; object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database -&gt; index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index -&gt; 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><div class="preface" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id394089"></a>Preface</h2></div></div></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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2command-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]3to fetch and study a project using git—read these chapters to learn how
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]4to build and test a particular version of a software project, search for
5regressions, and so on.</p><p>People needing to do actual development will also want to read
Junio C Hamanoec87f522008-12-10 08:35:25[diff] [blame]6<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]7pages, or <a class="ulink" href="git-help.html" target="_top">git-help(1)</a> command. For example, for the command
8"git clone &lt;repo&gt;", you can either use:</p><div class="literallayout"><p>$ man git-clone</p></div><p>or:</p><div class="literallayout"><p>$ git help clone</p></div><p>With the latter, you can use the manual viewer of your choice; see
9<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]10without 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 Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]11complete.</p></div><div class="chapter" lang="en"><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" lang="en"><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]12read 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 Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]13download a copy of an existing repository. If you don't already have a
14project in mind, here are some interesting examples:</p><div class="literallayout"><p>        # git itself (approx. 10MB download):<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]15$ git clone git://git.kernel.org/pub/scm/git/git.git<br>
Junio C Hamano4fbdd442009-01-06 05:56:24[diff] [blame]16        # the Linux kernel (approx. 150MB download):<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]17$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git</p></div><p>The initial clone may be time-consuming for a large project, but you
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]18will only need to clone once.</p><p>The clone command creates a new directory named after the project ("git"
19or "linux-2.6" in the examples above). After you cd into this
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]20directory, you will see that it contains a copy of the project files,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]21called the <a class="link" href="#def_working_tree">working tree</a>, together with a special
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]22top-level directory named ".git", which contains all the information
23about the history of the project.</p></div><div class="section" lang="en"><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]24of files. It stores the history as a compressed collection of
25interrelated snapshots of the project's contents. In git each such
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]26version 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]27oldest to newest; instead, work may simultaneously proceed along
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]28parallel lines of development, called <a class="link" href="#def_branch">branches</a>, which may
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]29merge 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]30does this by keeping a list of <a class="link" href="#def_head">heads</a> which reference the
31latest commit on each branch; the <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a> command shows
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]32you the list of branch heads:</p><div class="literallayout"><p>$ git branch<br>
33* master</p></div><p>A freshly cloned repository contains a single branch head, by default
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]34named "master", with the working directory initialized to the state of
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]35the 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 Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]36references into the project's history, and can be listed using the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]37<a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> command:</p><div class="literallayout"><p>$ git tag -l<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]38v2.6.11<br>
39v2.6.11-tree<br>
40v2.6.12<br>
41v2.6.12-rc2<br>
42v2.6.12-rc3<br>
43v2.6.12-rc4<br>
44v2.6.12-rc5<br>
45v2.6.12-rc6<br>
46v2.6.13<br>
47...</p></div><p>Tags are expected to always point at the same version of a project,
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]48while 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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]49out using <a class="ulink" href="git-checkout.html" target="_top">git-checkout(1)</a>:</p><div class="literallayout"><p>$ git checkout -b new v2.6.13</p></div><p>The working directory then reflects the contents that the project had
50when it was tagged v2.6.13, and <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a> shows two
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]51branches, with an asterisk marking the currently checked-out branch:</p><div class="literallayout"><p>$ git branch<br>
52  master<br>
53* new</p></div><p>If you decide that you'd rather see version 2.6.17, you can modify
54the current branch to point at v2.6.17 instead, with</p><div class="literallayout"><p>$ git reset --hard v2.6.17</p></div><p>Note that if the current branch head was your only reference to a
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]55particular point in history, then resetting that branch may leave you
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]56with no way to find the history it used to point to; so use this command
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]57carefully.</p></div><div class="section" lang="en"><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]58The <a class="ulink" href="git-show.html" target="_top">git-show(1)</a> command shows the most recent commit on the
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]59current branch:</p><div class="literallayout"><p>$ git show<br>
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]60commit 17cf781661e6d38f737f15f53ab552f1e95960d7<br>
61Author: Linus Torvalds &lt;torvalds@ppc970.osdl.org.(none)&gt;<br>
62Date:   Tue Apr 19 14:11:06 2005 -0700<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]63<br>
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]64    Remove duplicate getenv(DB_ENVIRONMENT) call<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]65<br>
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]66    Noted by Tony Luck.<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]67<br>
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]68diff --git a/init-db.c b/init-db.c<br>
69index 65898fa..b002dc6 100644<br>
70--- a/init-db.c<br>
71+++ b/init-db.c<br>
72@@ -7,7 +7,7 @@<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]73<br>
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]74 int main(int argc, char **argv)<br>
75 {<br>
76-       char *sha1_dir = getenv(DB_ENVIRONMENT), *path;<br>
77+       char *sha1_dir, *path;<br>
78        int len, i;<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]79<br>
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]80        if (mkdir(".git", 0755) &lt; 0) {</p></div><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]81did, and why.</p><p>Every commit has a 40-hexdigit id, sometimes called the "object name" or the
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]82"SHA-1 id", shown on the first line of the "git show" output. You can usually
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]83refer to a commit by a shorter name, such as a tag or a branch name, but this
84longer name can also be useful. Most importantly, it is a globally unique
85name for this commit: so if you tell somebody else the object name (for
86example in email), then you are guaranteed that name will refer to the same
87commit in their repository that it does in yours (assuming their repository
88has that commit at all). Since the object name is computed as a hash over the
89contents of the commit, you are guaranteed that the commit can never change
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]90without 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]91history, including file data and directory contents, is stored in an object
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]92with a name that is a hash of its contents.</p><div class="section" lang="en"><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]93parent commit which shows what happened before this commit.
94Following the chain of parents will eventually take you back to the
95beginning of the project.</p><p>However, the commits do not form a simple list; git allows lines of
96development to diverge and then reconverge, and the point where two
97lines of development reconverge is called a "merge". The commit
98representing a merge can therefore have more than one parent, with
99each parent representing the most recent commit on one of the lines
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]100of 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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]101command; running gitk now on a git repository and looking for merge
102commits will help understand how the git organizes history.</p><p>In the following, we say that commit X is "reachable" from commit Y
103if commit X is an ancestor of commit Y. Equivalently, you could say
Junio C Hamanoa6387422007-08-25 03:54:27[diff] [blame]104that Y is a descendant of X, or that there is a chain of parents
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]105leading from commit Y to commit X.</p></div><div class="section" lang="en"><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]106below. Commits are shown as "o", and the links between them with
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]107lines drawn with - / and \. Time goes left to right:</p><pre class="literallayout"> o--o--o &lt;-- Branch A
108 /
109 o--o--o &lt;-- master
110 \
111 o--o--o &lt;-- Branch B</pre><p>If we need to talk about a particular commit, the character "o" may
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]112be replaced with another letter or number.</p></div><div class="section" lang="en"><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]113of development, and "branch head" (or just "head") to mean a reference
114to the most recent commit on a branch. In the example above, the branch
115head named "A" is a pointer to one particular commit, but we refer to
116the line of three commits leading up to that point as all being part of
117"branch A".</p><p>However, when no confusion will result, we often just use the term
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]118"branch" both for branches and for branch heads.</p></div></div><div class="section" lang="en"><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]119a summary of the commands:</p><div class="variablelist"><dl><dt><span class="term">
120git branch
121</span></dt><dd>
122 list all branches
123</dd><dt><span class="term">
124git branch &lt;branch&gt;
125</span></dt><dd>
126 create a new branch named &lt;branch&gt;, referencing the same
127 point in history as the current branch
128</dd><dt><span class="term">
129git branch &lt;branch&gt; &lt;start-point&gt;
130</span></dt><dd>
131 create a new branch named &lt;branch&gt;, referencing
132 &lt;start-point&gt;, which may be specified any way you like,
133 including using a branch name or a tag name
134</dd><dt><span class="term">
135git branch -d &lt;branch&gt;
136</span></dt><dd>
137 delete the branch &lt;branch&gt;; if the branch you are deleting
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]138 points to a commit which is not reachable from the current
139 branch, this command will fail with a warning.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]140</dd><dt><span class="term">
141git branch -D &lt;branch&gt;
142</span></dt><dd>
143 even if the branch points to a commit not reachable
144 from the current branch, you may know that that commit
145 is still reachable from some other branch or tag. In that
146 case it is safe to use this command to force git to delete
147 the branch.
148</dd><dt><span class="term">
149git checkout &lt;branch&gt;
150</span></dt><dd>
151 make the current branch &lt;branch&gt;, updating the working
152 directory to reflect the version referenced by &lt;branch&gt;
153</dd><dt><span class="term">
154git checkout -b &lt;new&gt; &lt;start-point&gt;
155</span></dt><dd>
156 create a new branch &lt;new&gt; referencing &lt;start-point&gt;, and
157 check it out.
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]158</dd></dl></div><p>The special symbol "HEAD" can always be used to refer to the current
159branch. In fact, git uses a file named "HEAD" in the .git directory to
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]160remember which branch is current:</p><div class="literallayout"><p>$ cat .git/HEAD<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]161ref: refs/heads/master</p></div></div><div class="section" lang="en"><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]162accept an arbitrary commit; for example, you can check out the commit
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]163referenced by a tag:</p><div class="literallayout"><p>$ git checkout v2.6.17<br>
164Note: moving to "v2.6.17" which isn't a local branch<br>
165If you want to create a new branch from this checkout, you may do so<br>
166(now or later) by using -b with the checkout command again. Example:<br>
167  git checkout -b &lt;new_branch_name&gt;<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]168HEAD is now at 427abfa... Linux v2.6.17</p></div><p>The HEAD then refers to the SHA-1 of the commit instead of to a branch,
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]169and git branch shows that you are no longer on a branch:</p><div class="literallayout"><p>$ cat .git/HEAD<br>
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]170427abfa28afedffadfca9dd8b067eb6d36bac53f<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]171$ git branch<br>
172* (no branch)<br>
173  master</p></div><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]174make up a name for the new branch. You can still create a new branch
175(or tag) for this version later if you decide to.</p></div><div class="section" lang="en"><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]176of the HEAD in the repository that you cloned from. That repository
177may also have had other branches, though, and your local repository
178keeps branches which track each of those remote branches, which you
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]179can view using the "-r" option to <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a>:</p><div class="literallayout"><p>$ git branch -r<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]180  origin/HEAD<br>
181  origin/html<br>
182  origin/maint<br>
183  origin/man<br>
184  origin/master<br>
185  origin/next<br>
186  origin/pu<br>
187  origin/todo</p></div><p>You cannot check out these remote-tracking branches, but you can
188examine them on a branch of your own, just as you would a tag:</p><div class="literallayout"><p>$ git checkout -b my-todo-copy origin/todo</p></div><p>Note that the name "origin" is just the name that git uses by default
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]189to refer to the repository that you cloned from.</p></div><div class="section" lang="en"><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
190commits. All references are named with a slash-separated path name
191starting with "refs"; the names we've been using so far are actually
192shorthand:</p><div class="itemizedlist"><ul type="disc"><li>
193The branch "test" is short for "refs/heads/test".
194</li><li>
195The tag "v2.6.18" is short for "refs/tags/v2.6.18".
196</li><li>
197"origin/master" is short for "refs/remotes/origin/master".
198</li></ul></div><p>The full name is occasionally useful if, for example, there ever
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]199exists a tag and a branch with the same name.</p><p>(Newly created refs are actually stored in the .git/refs directory,
200under the path given by their name. However, for efficiency reasons
201they may also be packed together in a single file; see
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]202<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]203to just using the name of that repository. So, for example, "origin"
204is 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]205the order it uses to decide which to choose when there are multiple
206references with the same shorthand name, see the "SPECIFYING
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]207REVISIONS" section of <a class="ulink" href="git-rev-parse.html" target="_top">git-rev-parse(1)</a>.</p></div><div class="section" lang="en"><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]208repository, creating new commits and advancing the branches to point
209at the new commits.</p><p>The command "git fetch", with no arguments, will update all of the
210remote-tracking branches to the latest version found in her
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]211repository. It will not touch any of your own branches—not even the
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]212"master" branch that was created for you on clone.</p></div><div class="section" lang="en"><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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]213cloned from, using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a>:</p><div class="literallayout"><p>$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]214$ git fetch linux-nfs<br>
215* refs/remotes/linux-nfs/master: storing branch 'master' ...<br>
216  commit: bf81b46</p></div><p>New remote-tracking branches will be stored under the shorthand name
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]217that you gave "git remote add", in this case linux-nfs:</p><div class="literallayout"><p>$ git branch -r<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]218linux-nfs/master<br>
219origin/master</p></div><p>If you run "git fetch &lt;remote&gt;" later, the tracking branches for the
220named &lt;remote&gt; will be updated.</p><p>If you examine the file .git/config, you will see that git has added
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]221a new stanza:</p><div class="literallayout"><p>$ cat .git/config<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]222...<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]223[remote "linux-nfs"]<br>
224        url = git://linux-nfs.org/pub/nfs-2.6.git<br>
225        fetch = +refs/heads/*:refs/remotes/linux-nfs/*<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]226...</p></div><p>This is what causes git to track the remote's branches; you may modify
227or delete these configuration options by editing .git/config with a
228text editor. (See the "CONFIGURATION FILE" section of
Junio C Hamanoec87f522008-12-10 08:35:25[diff] [blame]229<a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for details.)</p></div></div><div class="chapter" lang="en"><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-comments-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]230collection of files. It does this by storing compressed snapshots of
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]231the contents of a file hierarchy, together with "commits" which show
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]232the 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]233history of a project.</p><p>We start with one specialized tool that is useful for finding the
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]234commit that introduced a bug into a project.</p><div class="section" lang="en"><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]235"master" crashes. Sometimes the best way to find the cause of such a
236regression is to perform a brute-force search through the project's
237history to find the particular commit that caused the problem. The
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]238<a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> command can help you do this:</p><div class="literallayout"><p>$ git bisect start<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]239$ git bisect good v2.6.18<br>
240$ git bisect bad master<br>
241Bisecting: 3537 revisions left to test after this<br>
242[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]</p></div><p>If you run "git branch" at this point, you'll see that git has
Junio C Hamano9e395072008-07-31 22:11:21[diff] [blame]243temporarily moved you in "(no branch)". HEAD is now detached from any
244branch and points directly to a commit (with commit id 65934…) that
245is reachable from "master" but not from v2.6.18. Compile and test it,
246and see whether it crashes. Assume it does crash. Then:</p><div class="literallayout"><p>$ git bisect bad<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]247Bisecting: 1769 revisions left to test after this<br>
248[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings</p></div><p>checks out an older version. Continue like this, telling git at each
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]249stage whether the version it gives you is good or bad, and notice
250that the number of revisions left to test is cut approximately in
251half each time.</p><p>After about 13 tests (in this case), it will output the commit id of
252the guilty commit. You can then examine the commit with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]253<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 Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]254report with the commit id. Finally, run</p><div class="literallayout"><p>$ git bisect reset</p></div><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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]255point is just a suggestion, and you're free to try a different
256version if you think it would be a good idea. For example,
257occasionally you may land on a commit that broke something unrelated;
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]258run</p><div class="literallayout"><p>$ git bisect visualize</p></div><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]259says "bisect". Choose a safe-looking commit nearby, note its commit
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]260id, and check it out with:</p><div class="literallayout"><p>$ git reset --hard fb47ddb2db...</p></div><p>then test, run "bisect good" or "bisect bad" as appropriate, and
Junio C Hamano9e395072008-07-31 22:11:21[diff] [blame]261continue.</p><p>Instead of "git bisect visualize" and then "git reset —hard
262fb47ddb2db…", you might just want to tell git that you want to skip
263the current commit:</p><div class="literallayout"><p>$ git bisect skip</p></div><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]264bad 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]265test script that can tell a good from a bad commit. See
266<a class="ulink" href="git-bisect.html" target="_top">git-bisect(1)</a> for more information about this and other "git
267bisect" features.</p></div><div class="section" lang="en"><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 type="disc"><li>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]26840-hexdigit object name
269</li><li>
270branch name: refers to the commit at the head of the given
271 branch
272</li><li>
273tag name: refers to the commit pointed to by the given tag
274 (we've seen branches and tags are special cases of
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]275 <a class="link" href="#how-git-stores-references" title="Naming branches, tags, and other references">references</a>).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]276</li><li>
277HEAD: refers to the head of the current branch
278</li></ul></div><p>There are many more; see the "SPECIFYING REVISIONS" section of the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]279<a class="ulink" href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> man page for the complete list of ways to
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]280name revisions. Some examples:</p><div class="literallayout"><p>$ git show fb47ddb2 # the first few characters of the object name<br>
281                    # are usually enough to specify it uniquely<br>
282$ git show HEAD^    # the parent of the HEAD commit<br>
283$ git show HEAD^^   # the grandparent<br>
284$ git show HEAD~4   # the great-great-grandparent</p></div><p>Recall that merge commits may have more than one parent; by default,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]285^ and ~ follow the first parent listed in the commit, but you can
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]286also choose:</p><div class="literallayout"><p>$ git show HEAD^1   # show the first parent of HEAD<br>
287$ git show HEAD^2   # show the second parent of HEAD</p></div><p>In addition to HEAD, there are several other special names for
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]288commits:</p><p>Merges (to be discussed later), as well as operations such as
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]289<code class="literal">git reset</code>, which change the currently checked-out commit, generally
290set 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
291branch in FETCH_HEAD. For example, if you run <code class="literal">git fetch</code> without
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]292specifying a local branch as the target of the operation</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git theirbranch</p></div><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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]293which refers to the other branch that we're merging in to the current
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]294branch.</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]295occasionally useful for translating some name for a commit to the object
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]296name for that commit:</p><div class="literallayout"><p>$ git rev-parse origin<br>
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]297e05db0fd4f31dde7005f075a84f96b360d05984b</p></div></div><div class="section" lang="en"><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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]298running</p><div class="literallayout"><p>$ git tag stable-1 1b2e1d63ff</p></div><p>You can use stable-1 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]299comment with the tag, and possibly sign it cryptographically, then you
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]300should create a tag object instead; see the <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> man page
301for details.</p></div><div class="section" lang="en"><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]302own, it shows all commits reachable from the parent commit; but you
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]303can also make more specific requests:</p><div class="literallayout"><p>$ git log v2.5..        # commits since (not reachable from) v2.5<br>
304$ git log test..master  # commits reachable from master but not test<br>
305$ git log master..test  # ...reachable from test but not master<br>
306$ git log master...test # ...reachable from either test or master,<br>
307                        #    but not both<br>
308$ git log --since="2 weeks ago" # commits from the last 2 weeks<br>
309$ git log Makefile      # commits which modify Makefile<br>
310$ git log fs/           # ... which modify any file under fs/<br>
311$ git log -S'foo()'     # commits which add or remove any file data<br>
312                        # matching the string 'foo()'</p></div><p>And of course you can combine all of these; the following finds
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]313commits since v2.5 which touch the Makefile or any file under fs:</p><div class="literallayout"><p>$ git log v2.5.. Makefile fs/</p></div><p>You can also ask git log to show patches:</p><div class="literallayout"><p>$ git log -p</p></div><p>See the "—pretty" 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]314display options.</p><p>Note that git log starts with the most recent commit and works
315backwards through the parents; however, since git history can contain
Junio C Hamanoee1e4282007-02-04 08:32:04[diff] [blame]316multiple independent lines of development, the particular order that
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]317commits are listed in may be somewhat arbitrary.</p></div><div class="section" lang="en"><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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]318<a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a>:</p><div class="literallayout"><p>$ git diff master..test</p></div><p>That will produce the diff between the tips of the two branches. If
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]319you'd prefer to find the diff from their common ancestor to test, you
320can use three dots instead of two:</p><div class="literallayout"><p>$ git diff master...test</p></div><p>Sometimes what you want instead is a set of patches; for this you can
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]321use <a class="ulink" href="git-format-patch.html" target="_top">git-format-patch(1)</a>:</p><div class="literallayout"><p>$ git format-patch master..test</p></div><p>will generate a file with a patch for each commit reachable from test
Junio C Hamano393e57f2007-11-20 04:53:25[diff] [blame]322but not from master.</p></div><div class="section" lang="en"><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]323correct revision first. But sometimes it is more convenient to be
324able to view an old version of a single file without checking
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]325anything out; this command does that:</p><div class="literallayout"><p>$ git show v2.5:fs/locks.c</p></div><p>Before the colon may be anything that names a commit, and after it
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]326may be any path to a file tracked by git.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="history-examples"></a>Examples</h2></div></div></div><div class="section" lang="en"><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 "mybranch"
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]327since it diverged from "origin":</p><div class="literallayout"><p>$ git log --pretty=oneline origin..mybranch | wc -l</p></div><p>Alternatively, you may often see this sort of thing done with the
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]328lower-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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]329of all the given commits:</p><div class="literallayout"><p>$ git rev-list origin..mybranch | wc -l</p></div></div><div class="section" lang="en"><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
330in history.</p><div class="literallayout"><p>$ git diff origin..master</p></div><p>will tell you whether the contents of the project are the same at the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]331two branches; in theory, however, it's possible that the same project
332contents could have been arrived at by two different historical
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]333routes. You could compare the object names:</p><div class="literallayout"><p>$ git rev-list origin<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]334e05db0fd4f31dde7005f075a84f96b360d05984b<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]335$ git rev-list master<br>
336e05db0fd4f31dde7005f075a84f96b360d05984b</p></div><p>Or you could recall that the … operator selects all commits
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]337contained reachable from either one reference or the other but not
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]338both: so</p><div class="literallayout"><p>$ git log origin...master</p></div><p>will return no commits when the two branches are equal.</p></div><div class="section" lang="en"><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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]339You'd like to find the earliest tagged release that contains that
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]340fix.</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]341after commit e05db0fd, then there could be multiple "earliest" tagged
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]342releases.</p><p>You could just visually inspect the commits since e05db0fd:</p><div class="literallayout"><p>$ gitk e05db0fd..</p></div><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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]343name based on any tag it finds pointing to one of the commit's
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]344descendants:</p><div class="literallayout"><p>$ git name-rev --tags e05db0fd<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]345e05db0fd tags/v1.5.0-rc1^0~23</p></div><p>The <a class="ulink" href="git-describe.html" target="_top">git-describe(1)</a> command does the opposite, naming the
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]346revision using a tag on which the given commit is based:</p><div class="literallayout"><p>$ git describe e05db0fd<br>
Junio C Hamano4c6aa8a2007-04-04 08:56:37[diff] [blame]347v1.5.0-rc0-260-ge05db0f</p></div><p>but that may sometimes help you guess which tags might come after the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]348given commit.</p><p>If you just want to verify whether a given tagged version contains a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]349given commit, you could use <a class="ulink" href="git-merge-base.html" target="_top">git-merge-base(1)</a>:</p><div class="literallayout"><p>$ git merge-base e05db0fd v1.5.0-rc1<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]350e05db0fd4f31dde7005f075a84f96b360d05984b</p></div><p>The merge-base command finds a common ancestor of the given commits,
351and always returns one or the other in the case where one is a
352descendant of the other; so the above output shows that e05db0fd
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]353actually is an ancestor of v1.5.0-rc1.</p><p>Alternatively, note that</p><div class="literallayout"><p>$ git log v1.5.0-rc1..e05db0fd</p></div><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]354because 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]355the commits reachable from its arguments with a display on the left-hand
356side that indicates which arguments that commit is reachable from. So,
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]357you can run something like</p><div class="literallayout"><p>$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2<br>
358! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]359available<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]360 ! [v1.5.0-rc0] GIT v1.5.0 preview<br>
361  ! [v1.5.0-rc1] GIT v1.5.0-rc1<br>
362   ! [v1.5.0-rc2] GIT v1.5.0-rc2<br>
363...</p></div><p>then search for a line that looks like</p><div class="literallayout"><p>+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]364available</p></div><p>Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]365from v1.5.0-rc2, but not from v1.5.0-rc0.</p></div><div class="section" lang="en"><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
366head named "master" but not from any other head in your repository.</p><p>We can list all the heads in this repository with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]367<a class="ulink" href="git-show-ref.html" target="_top">git-show-ref(1)</a>:</p><div class="literallayout"><p>$ git show-ref --heads<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]368bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial<br>
369db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint<br>
370a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master<br>
37124dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2<br>
3721e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes</p></div><p>We can get just the branch-head names, and remove "master", with
373the help of the standard utilities cut and grep:</p><div class="literallayout"><p>$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]374refs/heads/core-tutorial<br>
375refs/heads/maint<br>
376refs/heads/tutorial-2<br>
377refs/heads/tutorial-fixes</p></div><p>And then we can ask to see all the commits reachable from master
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]378but not from these other heads:</p><div class="literallayout"><p>$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |<br>
379                                grep -v '^refs/heads/master' )</p></div><p>Obviously, endless variations are possible; for example, to see all
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]380commits reachable from some head but not from any tag in the repository:</p><div class="literallayout"><p>$ gitk $( git show-ref --heads ) --not  $( git show-ref --tags )</p></div><p>(See <a class="ulink" href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> for explanations of commit-selecting
381syntax such as <code class="literal">—not</code>.)</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="making-a-release"></a>Creating a changelog and tarball for a software release</h3></div></div></div><p>The <a class="ulink" href="git-archive.html" target="_top">git-archive(1)</a> command can create a tar or zip archive from
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]382any version of a project; for example:</p><div class="literallayout"><p>$ git archive --format=tar --prefix=project/ HEAD | gzip &gt;latest.tar.gz</p></div><p>will use HEAD to produce a tar archive in which each filename is
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]383preceded by "project/".</p><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]384to simultaneously make a changelog to include in the release
385announcement.</p><p>Linus Torvalds, for example, makes new kernel releases by tagging them,
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]386then running:</p><div class="literallayout"><p>$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7</p></div><p>where release-script is a shell script that looks like:</p><div class="literallayout"><p>#!/bin/sh<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]387stable="$1"<br>
388last="$2"<br>
389new="$3"<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]390echo "# git tag v$new"<br>
391echo "git archive --prefix=linux-$new/ v$new | gzip -9 &gt; ../linux-$new.tar.gz"<br>
392echo "git diff v$stable v$new | gzip -9 &gt; ../patch-$new.gz"<br>
393echo "git log --no-merges v$new ^v$last &gt; ../ChangeLog-$new"<br>
394echo "git shortlog --no-merges v$new ^v$last &gt; ../ShortLog"<br>
395echo "git diff --stat --summary -M v$last v$new &gt; ../diffstat-$new"</p></div><p>and then he just cut-and-pastes the output commands after verifying that
Junio C Hamanoec87f522008-12-10 08:35:25[diff] [blame]396they look OK.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="Finding-comments-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]397file such that it contained the given content either before or after the
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]398commit. You can find out with this:</p><div class="literallayout"><p>$  git log --raw --abbrev=40 --pretty=oneline |<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]399        grep -B 1 `git hash-object filename`</p></div><p>Figuring out why this works is left as an exercise to the (advanced)
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]400student. 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 Hamanoec87f522008-12-10 08:35:25[diff] [blame]401<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" lang="en"><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" lang="en"><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. The
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]402easiest way to do so is to make sure the following lines appear in a
403file named .gitconfig in your home directory:</p><div class="literallayout"><p>[user]<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]404        name = Your Name Comes Here<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]405        email = you@yourdomain.example.com</p></div><p>(See the "CONFIGURATION FILE" section of <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]406details on the configuration file.)</p></div><div class="section" lang="en"><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><div class="literallayout"><p>$ mkdir project<br>
407$ cd project<br>
Junio C Hamano4fbdd442009-01-06 05:56:24[diff] [blame]408$ git init</p></div><p>If you have some initial content (say, a tarball):</p><div class="literallayout"><p>$ tar xzvf project.tar.gz<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]409$ cd project<br>
410$ git init<br>
411$ git add . # include everything below ./ in the first commit:<br>
412$ git commit</p></div></div><div class="section" lang="en"><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 type="1"><li>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]413Making some changes to the working directory using your
414 favorite editor.
415</li><li>
416Telling git about your changes.
417</li><li>
418Creating the commit using the content you told git about
419 in step 2.
420</li></ol></div><p>In practice, you can interleave and repeat steps 1 and 2 as many
421times as you want: in order to keep track of what you want committed
422at step 3, git maintains a snapshot of the tree's contents in a
423special staging area called "the index."</p><p>At the beginning, the content of the index will be identical to
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]424that of the HEAD. The command "git diff —cached", which shows
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]425the difference between the HEAD and the index, should therefore
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]426produce no output at that point.</p><p>Modifying the index is easy:</p><p>To update the index with the new contents of a modified file, use</p><div class="literallayout"><p>$ git add path/to/file</p></div><p>To add the contents of a new file to the index, use</p><div class="literallayout"><p>$ git add path/to/file</p></div><p>To remove a file from the index and from the working tree,</p><div class="literallayout"><p>$ git rm path/to/file</p></div><p>After each step you can verify that</p><div class="literallayout"><p>$ git diff --cached</p></div><p>always shows the difference between the HEAD and the index file—this
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]427is what you'd commit if you created the commit now—and that</p><div class="literallayout"><p>$ git diff</p></div><p>shows the difference between the working tree and the index file.</p><p>Note that "git add" always adds just the current contents of a file
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]428to the index; further changes to the same file will be ignored unless
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]429you run <code class="literal">git add</code> on the file again.</p><p>When you're ready, just run</p><div class="literallayout"><p>$ git commit</p></div><p>and git will prompt you for a commit message and then create the new
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]430commit. Check to make sure it looks like what you expected with</p><div class="literallayout"><p>$ git show</p></div><p>As a special shortcut,</p><div class="literallayout"><p>$ git commit -a</p></div><p>will update the index with any files that you've modified or removed
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]431and create a commit, all in one step.</p><p>A number of commands are useful for keeping track of what you're
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]432about to commit:</p><div class="literallayout"><p>$ git diff --cached # difference between HEAD and the index; what<br>
433                    # would be committed if you ran "commit" now.<br>
434$ git diff          # difference between the index file and your<br>
435                    # working directory; changes that would not<br>
436                    # be included if you ran "commit" now.<br>
437$ git diff HEAD     # difference between HEAD and working tree; what<br>
438                    # would be committed if you ran "commit -a" now.<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]439$ git status        # a brief per-file summary of the above.</p></div><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]440the index and the working tree files, and individually select diff hunks
441for inclusion in the index (by right-clicking on the diff hunk and
442choosing "Stage Hunk For Commit").</p></div><div class="section" lang="en"><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]443with a single short (less than 50 character) line summarizing the
444change, followed by a blank line and then a more thorough
445description. Tools that turn commits into email, for example, use
446the first line on the Subject line and the rest of the commit in the
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]447body.</p></div><div class="section" lang="en"><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.
448This typically includes files generated by a build process or temporary
449backup 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]450is 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]451annoying to have these untracked files lying around; e.g. they make
Junio C Hamanoea82cff2009-03-18 01:54:48[diff] [blame]452<code class="literal">git add .</code> practically useless, and they keep showing up in the output of
453<code class="literal">git status</code>.</p><p>You can tell git to ignore certain files by creating a file called .gitignore
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]454in the top level of your working directory, with contents such as:</p><div class="literallayout"><p># Lines starting with '#' are considered comments.<br>
455# Ignore any file named foo.txt.<br>
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]456foo.txt<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]457# Ignore (generated) html files,<br>
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]458*.html<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]459# except foo.html which is maintained by hand.<br>
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]460!foo.html<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]461# Ignore objects and archives.<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]462*.[oa]</p></div><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]463also place .gitignore files in other directories in your working tree, and they
464will apply to those directories and their subdirectories. The <code class="literal">.gitignore</code>
465files can be added to your repository like any other files (just run <code class="literal">git add
466.gitignore</code> and <code class="literal">git commit</code>, as usual), which is convenient when the exclude
467patterns (such as patterns matching build output files) would also make sense
468for other users who clone your repository.</p><p>If you wish the exclude patterns to affect only certain repositories
469(instead of every repository for a given project), you may instead put
470them in a file in your repository named .git/info/exclude, or in any file
471specified by the <code class="literal">core.excludesfile</code> configuration variable. Some git
472commands can also take exclude patterns directly on the command line.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]473See <a class="ulink" href="gitignore.html" target="_top">gitignore(5)</a> for the details.</p></div><div class="section" lang="en"><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
474<a class="ulink" href="git-merge.html" target="_top">git-merge(1)</a>:</p><div class="literallayout"><p>$ git merge branchname</p></div><p>merges the development in the branch "branchname" into the current
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]475branch. If there are conflicts—for example, if the same file is
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]476modified in two different ways in the remote branch and the local
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]477branch—then you are warned; the output may look something like this:</p><div class="literallayout"><p>$ git merge next<br>
478 100% (4/4) done<br>
479Auto-merged file.txt<br>
480CONFLICT (content): Merge conflict in file.txt<br>
481Automatic merge failed; fix conflicts and then commit the result.</p></div><p>Conflict markers are left in the problematic files, and after
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]482you resolve the conflicts manually, you can update the index
483with the contents and run git commit, as you normally would when
484creating a new file.</p><p>If you examine the resulting commit using gitk, you will see that it
485has two parents, one pointing to the top of the current branch, and
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]486one to the top of the other branch.</p></div><div class="section" lang="en"><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]487the working tree in a special state that gives you all the
488information 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]489resolve the problem and update the index, <a class="ulink" href="git-commit.html" target="_top">git-commit(1)</a> will
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]490fail:</p><div class="literallayout"><p>$ git commit<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]491file.txt: needs merge</p></div><p>Also, <a class="ulink" href="git-status.html" target="_top">git-status(1)</a> will list those files as "unmerged", and the
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]492files with conflicts will have conflict markers added, like this:</p><div class="literallayout"><p>&lt;&lt;&lt;&lt;&lt;&lt;&lt; HEAD:file.txt<br>
493Hello world<br>
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]494=======<br>
495Goodbye<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]496&gt;&gt;&gt;&gt;&gt;&gt;&gt; 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</p></div><p>All you need to do is edit the files to resolve the conflicts, and then</p><div class="literallayout"><p>$ git add file.txt<br>
497$ git commit</p></div><p>Note that the commit message will already be filled in for you with
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]498some information about the merge. Normally you can just use this
499default message unchanged, but you may add additional commentary of
500your own if desired.</p><p>The above is all you need to know to resolve a simple merge. But git
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]501also provides more information to help resolve conflicts:</p><div class="section" lang="en"><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]502already added to the index file, so <a class="ulink" href="git-diff.html" target="_top">git-diff(1)</a> shows only
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]503the conflicts. It uses an unusual syntax:</p><div class="literallayout"><p>$ git diff<br>
504diff --cc file.txt<br>
505index 802992c,2b60207..0000000<br>
506--- a/file.txt<br>
507+++ b/file.txt<br>
508@@@ -1,1 -1,1 +1,5 @@@<br>
509++&lt;&lt;&lt;&lt;&lt;&lt;&lt; HEAD:file.txt<br>
510 +Hello world<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]511++=======<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]512+ Goodbye<br>
513++&gt;&gt;&gt;&gt;&gt;&gt;&gt; 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</p></div><p>Recall that the commit which will be committed after we resolve this
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]514conflict will have two parents instead of the usual one: one parent
515will be HEAD, the tip of the current branch; the other will be the
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]516tip 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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]517these three "file stages" represents a different version of the file:</p><div class="literallayout"><p>$ git show :1:file.txt  # the file in a common ancestor of both branches<br>
Junio C Hamano6fb124c2008-06-13 10:04:01[diff] [blame]518$ git show :2:file.txt  # the version from HEAD.<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]519$ git show :3:file.txt  # the version from MERGE_HEAD.</p></div><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]520three-way diff between the conflicted merge results in the work tree with
521stages 2 and 3 to show only hunks whose contents come from both sides,
522mixed (in other words, when a hunk's merge results come only from stage 2,
523that 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]524file.txt and the stage 2 and stage 3 versions. So instead of preceding
525each line by a single "+" or "-", it now uses two columns: the first
526column is used for differences between the first parent and the working
527directory copy, and the second for differences between the second parent
528and the working directory copy. (See the "COMBINED DIFF FORMAT" section
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]529of <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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]530index), the diff will look like:</p><div class="literallayout"><p>$ git diff<br>
531diff --cc file.txt<br>
532index 802992c,2b60207..0000000<br>
533--- a/file.txt<br>
534+++ b/file.txt<br>
535@@@ -1,1 -1,1 +1,1 @@@<br>
536- Hello world<br>
537 -Goodbye<br>
538++Goodbye world</p></div><p>This shows that our resolved version deleted "Hello world" from the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]539first parent, deleted "Goodbye" from the second parent, and added
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]540"Goodbye world", which was previously absent from both.</p><p>Some special diff options allow diffing the working directory against
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]541any of these stages:</p><div class="literallayout"><p>$ git diff -1 file.txt          # diff against stage 1<br>
542$ git diff --base file.txt      # same as the above<br>
543$ git diff -2 file.txt          # diff against stage 2<br>
544$ git diff --ours file.txt      # same as the above<br>
545$ git diff -3 file.txt          # diff against stage 3<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]546$ git diff --theirs file.txt    # same as the above.</p></div><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
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]547for merges:</p><div class="literallayout"><p>$ git log --merge<br>
548$ gitk --merge</p></div><p>These will display all commits which exist only on HEAD or on
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]549MERGE_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 Hamano4fbdd442009-01-06 05:56:24[diff] [blame]550unmerged 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><div class="literallayout"><p>$ git add file.txt</p></div><p>the different stages of that file will be "collapsed", after which
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]551<code class="literal">git diff</code> will (by default) no longer show diffs for that file.</p></div></div><div class="section" lang="en"><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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]552away, you can always return to the pre-merge state with</p><div class="literallayout"><p>$ git reset --hard HEAD</p></div><p>Or, if you've already committed the merge that you want to throw away,</p><div class="literallayout"><p>$ git reset --hard ORIG_HEAD</p></div><p>However, this last command can be dangerous in some cases—never
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]553throw away a commit you have already committed if that commit may
554itself have been merged into another branch, as doing so may confuse
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]555further merges.</p></div><div class="section" lang="en"><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]556differently. Normally, a merge results in a merge commit, with two
557parents, one pointing at each of the two lines of development that
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]558were merged.</p><p>However, if the current branch is a descendant of the other—so every
559commit present in the one is already contained in the other—then git
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]560just performs a "fast forward"; the head of the current branch is moved
561forward to point at the head of the merged-in branch, without any new
562commits being created.</p></div><div class="section" lang="en"><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]563mistake, you can return the entire working tree to the last committed
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]564state with</p><div class="literallayout"><p>$ git reset --hard HEAD</p></div><p>If you make a commit that you later wish you hadn't, there are two
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]565fundamentally different ways to fix the problem:</p><div class="orderedlist"><ol type="1"><li>
566You can create a new commit that undoes whatever was done
Junio C Hamano8c5802d2007-11-15 00:13:36[diff] [blame]567 by the old commit. This is the correct thing if your
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]568 mistake has already been made public.
569</li><li>
570You can go back and modify the old commit. You should
571 never do this if you have already made the history public;
572 git does not normally expect the "history" of a project to
573 change, and cannot correctly perform repeated merges from
574 a branch that has had its history changed.
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]575</li></ol></div><div class="section" lang="en"><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]576just pass the <a class="ulink" href="git-revert.html" target="_top">git-revert(1)</a> command a reference to the bad
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]577commit; for example, to revert the most recent commit:</p><div class="literallayout"><p>$ git revert HEAD</p></div><p>This will create a new commit which undoes the change in HEAD. You
578will 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><div class="literallayout"><p>$ git revert HEAD^</p></div><p>In this case git will attempt to undo the old change while leaving
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]579intact any changes made since then. If more recent changes overlap
580with the changes to be reverted, then you will be asked to fix
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]581conflicts 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" lang="en"><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]582yet made that commit public, then you may just
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]583<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]584can edit the working directory and update the index to fix your
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]585mistake, 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><div class="literallayout"><p>$ git commit --amend</p></div><p>which will replace the old commit by a new commit incorporating your
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]586changes, 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]587been 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]588that 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]589this is an advanced topic to be left for
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]590<a class="link" href="#cleaning-up-history" title="Chapter 5. Rewriting history and maintaining patch series">another chapter</a>.</p></div><div class="section" lang="en"><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]591useful to check out an older version of a particular file using
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]592<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]593branches, but it has quite different behavior if it is given a path
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]594name: the command</p><div class="literallayout"><p>$ git checkout HEAD^ path/to/file</p></div><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]595also 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
596modifying the working directory, you can do that with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]597<a class="ulink" href="git-show.html" target="_top">git-show(1)</a>:</p><div class="literallayout"><p>$ git show HEAD^:path/to/file</p></div><p>which will display the given version of the file.</p></div><div class="section" lang="en"><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]598find an unrelated but obvious and trivial bug. You would like to fix it
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]599before 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]600state of your work, and after fixing the bug (or, optionally after doing
601so on a different branch and then coming back), unstash the
Junio C Hamano78502452009-02-04 16:53:50[diff] [blame]602work-in-progress changes.</p><div class="literallayout"><p>$ git stash save "work in progress for foo feature"</p></div><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]603reset your working tree and the index to match the tip of your
604current branch. Then you can make your fix as usual.</p><div class="literallayout"><p>... edit and test ...<br>
605$ git commit -a -m "blorpl: typofix"</p></div><p>After that, you can go back to what you were working on with
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]606<code class="literal">git stash pop</code>:</p><div class="literallayout"><p>$ git stash pop</p></div></div></div><div class="section" lang="en"><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 Hamano764a6672007-10-23 01:23:31[diff] [blame]607information from taking up too much space on disk or in memory.</p><p>This compression is not performed automatically. Therefore you
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]608should occasionally run <a class="ulink" href="git-gc.html" target="_top">git-gc(1)</a>:</p><div class="literallayout"><p>$ git gc</p></div><p>to recompress the archive. This can be very time-consuming, so
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]609you may prefer to run <code class="literal">git gc</code> when you are not doing other work.</p></div><div class="section" lang="en"><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" lang="en"><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]610on the repository, and reports on any problems. This may take some
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]611time. The most common warning by far is about "dangling" objects:</p><div class="literallayout"><p>$ git fsck<br>
612dangling commit 7281251ddd2a61e38657c827739c57015671a6b3<br>
613dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63<br>
614dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5<br>
615dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb<br>
616dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f<br>
617dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e<br>
618dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085<br>
619dangling tree b24c2473f1fd3d91352a624795be026d64c8841f<br>
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]620...</p></div><p>Dangling objects are not a problem. At worst they may take up a little
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]621extra disk space. They can sometimes provide a last-resort method for
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]622recovering lost work—see <a class="xref" href="#dangling-objects" title="Dangling objects">the section called “Dangling objects”</a> for details.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="recovering-lost-changes"></a>Recovering lost changes</h3></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="reflogs"></a>Reflogs</h4></div></div></div><p>Say you modify a branch with <code class="literal"><a class="ulink" href="git-reset.html" target="_top">git-reset(1)</a> —hard</code>, and then
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]623realize that the branch was the only reference you had to that point in
624history.</p><p>Fortunately, git also keeps a log, called a "reflog", of all the
625previous values of each branch. So in this case you can still find the
Junio C Hamano63777e22007-11-17 20:52:16[diff] [blame]626old history using, for example,</p><div class="literallayout"><p>$ git log master@{1}</p></div><p>This lists the commits reachable from the previous version of the
627"master" branch head. This syntax can be used with any git command
628that accepts a commit, not just with git log. Some other examples:</p><div class="literallayout"><p>$ git show master@{2}           # See where the branch pointed 2,<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]629$ git show master@{3}           # 3, ... changes ago.<br>
630$ gitk master@{yesterday}       # See where it pointed yesterday,<br>
631$ gitk master@{"1 week ago"}    # ... or last week<br>
632$ git log --walk-reflogs master # show reflog entries for master</p></div><p>A separate reflog is kept for the HEAD, so</p><div class="literallayout"><p>$ git show HEAD@{"1 week ago"}</p></div><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]633pointed to one week ago. This allows you to see the history of what
634you'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]635pruned. 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]636how to control this pruning, and see the "SPECIFYING REVISIONS"
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]637section of <a class="ulink" href="git-rev-parse.html" target="_top">git-rev-parse(1)</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]638While normal history is shared by every repository that works on the
639same project, the reflog history is not shared: it tells you only about
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]640how the branches in your local repository have changed over time.</p></div><div class="section" lang="en"><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,
641suppose you delete a branch, then realize you need the history it
642contained. The reflog is also deleted; however, if you have not yet
643pruned the repository, then you may still be able to find the lost
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]644commits in the dangling objects that <code class="literal">git fsck</code> reports. See
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]645<a class="xref" href="#dangling-objects" title="Dangling objects">the section called “Dangling objects”</a> for the details.</p><div class="literallayout"><p>$ git fsck<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]646dangling commit 7281251ddd2a61e38657c827739c57015671a6b3<br>
647dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63<br>
648dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5<br>
Junio C Hamano39381a72007-02-02 07:35:15[diff] [blame]649...</p></div><p>You can examine
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]650one of those dangling commits with, for example,</p><div class="literallayout"><p>$ gitk 7281251ddd --not --all</p></div><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]651history that is described by the dangling commit(s), but not the
652history that is described by all your existing branches and tags. Thus
653you get exactly the history reachable from that commit that is lost.
654(And notice that it might not be just one commit: we only report the
655"tip of the line" as being dangling, but there might be a whole deep
Junio C Hamanodb911ee2007-02-28 08:13:52[diff] [blame]656and complex commit history that was dropped.)</p><p>If you decide you want the history back, you can always create a new
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]657reference pointing to it, for example, a new branch:</p><div class="literallayout"><p>$ git branch recovered-branch 7281251ddd</p></div><p>Other types of dangling objects (blobs and trees) are also possible, and
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]658dangling objects can arise in other situations.</p></div></div></div></div><div class="chapter" lang="en"><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" lang="en"><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 make a few changes of your own, you
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]659may wish to check the original repository for updates and merge them
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]660into 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]661and how to merge two branches. So you can merge in changes from the
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]662original repository's master branch with:</p><div class="literallayout"><p>$ git fetch<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]663$ git merge origin/master</p></div><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 Hamano4cd1c0e2007-08-06 04:39:14[diff] [blame]664one step:</p><div class="literallayout"><p>$ git pull origin master</p></div><p>In fact, if you have "master" checked out, then by default "git pull"
665merges from the HEAD branch of the origin repository. So often you can
666accomplish the above with just a simple</p><div class="literallayout"><p>$ git pull</p></div><p>More generally, a branch that is created from a remote branch will pull
667by default from that branch. See the descriptions of the
668branch.&lt;name&gt;.remote and branch.&lt;name&gt;.merge options in
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]669<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
670<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, "git pull" also helps you by
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]671producing a default commit message documenting the branch and
672repository that you pulled from.</p><p>(But note that no such commit will be created in the case of a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]673<a class="link" href="#fast-forwards" title="Fast-forward merges">fast forward</a>; instead, your branch will just be
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]674updated to point to the latest commit from the upstream branch.)</p><p>The <code class="literal">git pull</code> command can also be given "." as the "remote" repository,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]675in which case it just merges in a branch from the current repository; so
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]676the commands</p><div class="literallayout"><p>$ git pull . branch<br>
677$ git merge branch</p></div><p>are roughly equivalent. The former is actually very commonly used.</p></div><div class="section" lang="en"><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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]678just 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><div class="literallayout"><p>$ git format-patch origin</p></div><p>will produce a numbered series of files in the current directory, one
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]679for each patch in the current branch but not in origin/HEAD.</p><p>You can then import these into your mail client and send them by
680hand. However, if you have a lot to send at once, you may prefer to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]681use 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]682Consult the mailing list for your project first to determine how they
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]683prefer such patches be handled.</p></div><div class="section" lang="en"><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]684"apply mailbox"), for importing such an emailed series of patches.
685Just save all of the patch-containing messages, in order, into a
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]686single mailbox file, say "patches.mbox", then run</p><div class="literallayout"><p>$ git am -3 patches.mbox</p></div><p>Git will apply each patch in order; if any conflicts are found, it
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]687will stop, and you can fix the conflicts as described in
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]688"<a class="link" href="#resolving-a-merge" title="Resolving a merge">Resolving a merge</a>". (The "-3" option tells
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]689git to perform a merge; if you would prefer it just to abort and
690leave 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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]691resolution, instead of creating a new commit, just run</p><div class="literallayout"><p>$ git am --resolved</p></div><p>and git will create the commit for you and continue applying the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]692remaining patches from the mailbox.</p><p>The final result will be a series of commits, one for each patch in
693the original mailbox, with authorship and commit log message each
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]694taken from the message containing each patch.</p></div><div class="section" lang="en"><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
695of that project to pull the changes from your repository using
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]696<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]697updates from the "main" repository, but it works just as well in the
698other direction.</p><p>If you and the maintainer both have accounts on the same machine, then
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]699you can just pull changes from each other's repositories directly;
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]700commands that accept repository URLs as arguments will also accept a
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]701local directory name:</p><div class="literallayout"><p>$ git clone /path/to/repository<br>
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]702$ git pull /path/to/other/repository</p></div><p>or an ssh URL:</p><div class="literallayout"><p>$ git clone ssh://yourhost/~you/repository</p></div><p>For projects with few developers, or for synchronizing a few private
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]703repositories, 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]704repository (usually on a different host) for others to pull changes
705from. This is usually more convenient, and allows you to cleanly
706separate 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]707repository, but periodically "push" changes from your personal
708repository into your public repository, allowing other developers to
709pull from that repository. So the flow of changes, in a situation
710where there is one other developer with a public repository, looks
711like this:</p><pre class="literallayout"> you push
712your personal repo ------------------&gt; your public repo
713 ^ |
714 | |
715 | you pull | they pull
716 | |
717 | |
718 | they push V
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]719their public repo &lt;------------------- their repo</pre><p>We explain how to do this in the following sections.</p><div class="section" lang="en"><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 ~/proj. We
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]720first create a new clone of the repository and tell <code class="literal">git daemon</code> that it
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]721is meant to be public:</p><div class="literallayout"><p>$ git clone --bare ~/proj proj.git<br>
722$ touch proj.git/git-daemon-export-ok</p></div><p>The resulting directory proj.git contains a "bare" git repository—it is
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]723just the contents of the ".git" directory, without any files checked out
724around it.</p><p>Next, copy proj.git to the server where you plan to host the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]725public repository. You can use scp, rsync, or whatever is most
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]726convenient.</p></div><div class="section" lang="en"><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 Hamano764a6672007-10-23 01:23:31[diff] [blame]727directory to put the repository in, and what git:// URL it will appear
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]728at. You can then skip to the section
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]729"<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]730listen on port 9418. By default, it will allow access to any directory
731that looks like a git directory and contains the magic file
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]732git-daemon-export-ok. Passing some directory paths as <code class="literal">git daemon</code>
733arguments 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]734<a class="ulink" href="git-daemon.html" target="_top">git-daemon(1)</a> man page for details. (See especially the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]735examples section.)</p></div><div class="section" lang="en"><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
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]736host 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
737a directory that is exported by the web server, and make some
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]738adjustments to give web clients some extra information they need:</p><div class="literallayout"><p>$ mv proj.git /home/you/public_html/proj.git<br>
739$ cd proj.git<br>
740$ git --bare update-server-info<br>
Junio C Hamanoc96fb5a2008-08-12 06:59:38[diff] [blame]741$ mv hooks/post-update.sample hooks/post-update</p></div><p>(For an explanation of the last two lines, see
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]742<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 proj.git. Anybody else should then be able to
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]743clone or pull from that URL, for example with a command line like:</p><div class="literallayout"><p>$ git clone http://yourserver.com/~you/proj.git</p></div><p>(See also
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]744<a class="ulink" href="howto/setup-git-server-over-http.txt" target="_top">setup-git-server-over-http</a>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]745for a slightly more sophisticated setup using WebDAV which also
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]746allows pushing over http.)</p></div><div class="section" lang="en"><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
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]747<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]748maintainers to fetch your latest changes, but they do not allow write
749access, which you will need to update the public repository with the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]750latest 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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]751update the remote branch named "master" with the latest state of your
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]752branch named "master", run</p><div class="literallayout"><p>$ git push ssh://yourserver.com/~you/proj.git master:master</p></div><p>or just</p><div class="literallayout"><p>$ git push ssh://yourserver.com/~you/proj.git master</p></div><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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]753<a class="link" href="#fast-forwards" title="Fast-forward merges">fast forward</a>; see the following section for details on
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]754handling this case.</p><p>Note that the target of a "push" is normally a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]755<a class="link" href="#def_bare_repository">bare</a> repository. You can also push to a
Junio C Hamano2a8f6dc2007-07-09 08:48:38[diff] [blame]756repository that has a checked-out working tree, but the working tree
757will not be updated by the push. This may lead to unexpected results if
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]758the branch you push to is the currently checked-out branch!</p><p>As with <code class="literal">git fetch</code>, you may also set up configuration options to
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]759save typing; so, for example, after</p><div class="literallayout"><p>$ cat &gt;&gt;.git/config &lt;&lt;EOF<br>
760[remote "public-repo"]<br>
761        url = ssh://yourserver.com/~you/proj.git<br>
762EOF</p></div><p>you should be able to perform the above push with just</p><div class="literallayout"><p>$ git push public-repo master</p></div><p>See the explanations of the remote.&lt;name&gt;.url, branch.&lt;name&gt;.remote,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]763and remote.&lt;name&gt;.push options in <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for
764details.</p></div><div class="section" lang="en"><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 Hamanoce3650e2007-11-26 04:20:11[diff] [blame]765remote branch, then it will fail with an error like:</p><div class="literallayout"><p>error: remote 'refs/heads/master' is not an ancestor of<br>
766 local  'refs/heads/master'.<br>
767 Maybe you are not up-to-date and need to pull first?<br>
768error: failed to push to 'ssh://yourserver.com/~you/proj.git'</p></div><p>This can happen, for example, if you:</p><div class="itemizedlist"><ul type="disc"><li>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]769use <code class="literal">git reset —hard</code> to remove already-published commits, or
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]770</li><li>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]771use <code class="literal">git commit —amend</code> to replace already-published commits
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]772 (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 Hamanoce3650e2007-11-26 04:20:11[diff] [blame]773</li><li>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]774use <code class="literal">git rebase</code> to rebase any already-published commits (as
775 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>).
776</li></ul></div><p>You may force <code class="literal">git push</code> to perform the update anyway by preceding the
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]777branch name with a plus sign:</p><div class="literallayout"><p>$ git push ssh://yourserver.com/~you/proj.git +master</p></div><p>Normally whenever a branch head in a public repository is modified, it
Junio C Hamano878cc1e2007-12-14 08:35:13[diff] [blame]778is modified to point to a descendant of the commit that it pointed to
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]779before. By forcing a push in this situation, you break that convention.
Junio C Hamanoec87f522008-12-10 08:35:25[diff] [blame]780(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]781way to publish a work-in-progress patch series, and it is an acceptable
782compromise as long as you warn other developers that this is how you
783intend to manage the branch.</p><p>It's also possible for a push to fail in this way when other people have
784the right to push to the same repository. In that case, the correct
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]785solution is to retry the push after first updating your work: either by a
786pull, or by a fetch followed by a rebase; see the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]787<a class="link" href="#setting-up-a-shared-repository" title="Setting up a shared repository">next section</a> and
788<a class="ulink" href="gitcvs-migration.html" target="_top">gitcvs-migration(7)</a> for more.</p></div><div class="section" lang="en"><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]789commonly used in CVS, where several developers with special rights
790all push to and pull from a single shared repository. See
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]791<a class="ulink" href="gitcvs-migration.html" target="_top">gitcvs-migration(7)</a> for instructions on how to
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]792set this up.</p><p>However, while there is nothing wrong with git's support for shared
793repositories, this mode of operation is not generally recommended,
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]794simply because the mode of collaboration that git supports—by
795exchanging patches and pulling from public repositories—has so many
Junio C Hamanoed7f4f62007-05-20 09:09:09[diff] [blame]796advantages over the central shared repository:</p><div class="itemizedlist"><ul type="disc"><li>
797Git's ability to quickly import and merge patches allows a
798 single maintainer to process incoming changes even at very
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]799 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]800 an easy way for that maintainer to delegate this job to other
801 maintainers while still allowing optional review of incoming
802 changes.
803</li><li>
804Since every developer's repository has the same complete copy
805 of the project history, no repository is special, and it is
806 trivial for another developer to take over maintenance of a
807 project, either by mutual agreement, or because a maintainer
808 becomes unresponsive or difficult to work with.
809</li><li>
810The lack of a central group of "committers" means there is
811 less need for formal decisions about who is "in" and who is
812 "out".
813</li></ul></div></div><div class="section" lang="en"><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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]814project's files and history without having to install git; see the file
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]815gitweb/INSTALL in the git source tree for instructions on setting it up.</p></div></div><div class="section" lang="en"><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" lang="en"><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
816IA64 architecture for the Linux kernel.</p><p>He uses two public branches:</p><div class="itemizedlist"><ul type="disc"><li>
817A "test" tree into which patches are initially placed so that they
818 can get some exposure when integrated with other ongoing development.
819 This tree is available to Andrew for pulling into -mm whenever he
820 wants.
821</li><li>
822A "release" tree into which tested patches are moved for final sanity
823 checking, and as a vehicle to send them upstream to Linus (by sending
824 him a "please pull" request.)
825</li></ul></div><p>He also uses a set of temporary branches ("topic branches"), each
826containing a logical grouping of patches.</p><p>To set this up, first create your work tree by cloning Linus's public
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]827tree:</p><div class="literallayout"><p>$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git work<br>
828$ cd work</p></div><p>Linus's tree will be stored in the remote branch named origin/master,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]829and can be updated using <a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a>; you can track other
830public trees using <a class="ulink" href="git-remote.html" target="_top">git-remote(1)</a> to set up a "remote" and
831<a class="ulink" href="git-fetch.html" target="_top">git-fetch(1)</a> to keep them up-to-date; see
832<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]833at the current tip of origin/master branch, and should be set up (using
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]834the —track option to <a class="ulink" href="git-branch.html" target="_top">git-branch(1)</a>) to merge changes in from
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]835Linus by default.</p><div class="literallayout"><p>$ git branch --track test origin/master<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]836$ git branch --track release origin/master</p></div><p>These can be easily kept up to date using <a class="ulink" href="git-pull.html" target="_top">git-pull(1)</a>.</p><div class="literallayout"><p>$ git checkout test &amp;&amp; git pull<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]837$ git checkout release &amp;&amp; git pull</p></div><p>Important note! If you have any local changes in these branches, then
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]838this merge will create a commit object in the history (with no local
839changes git will simply do a "Fast forward" merge). Many people dislike
840the "noise" that this creates in the Linux history, so you should avoid
841doing this capriciously in the "release" branch, as these noisy commits
842will become part of the permanent history when you ask Linus to pull
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]843from 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]844make it easy to push both branches to your public tree. (See
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]845<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><div class="literallayout"><p>$ cat &gt;&gt; .git/config &lt;&lt;EOF<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]846[remote "mytree"]<br>
847        url =  master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git<br>
848        push = release<br>
849        push = test<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]850EOF</p></div><p>Then you can push both the test and release trees using
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]851<a class="ulink" href="git-push.html" target="_top">git-push(1)</a>:</p><div class="literallayout"><p>$ git push mytree</p></div><p>or push just one of the test and release branches using:</p><div class="literallayout"><p>$ git push mytree test</p></div><p>or</p><div class="literallayout"><p>$ git push mytree release</p></div><p>Now to apply some patches from the community. Think of a short
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]852snappy name for a branch to hold this patch (or related group of
853patches), and create a new branch from the current tip of Linus's
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]854branch:</p><div class="literallayout"><p>$ git checkout -b speed-up-spinlocks origin</p></div><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]855the patch is a multi-part series, then you should apply each as a separate
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]856commit to this branch.</p><div class="literallayout"><p>$ ... patch ... test  ... commit [ ... patch ... test ... commit ]*</p></div><p>When you are happy with the state of this change, you can pull it into the
857"test" branch in preparation to make it public:</p><div class="literallayout"><p>$ git checkout test &amp;&amp; git pull . speed-up-spinlocks</p></div><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]858spent 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
859same branch into the "release" tree ready to go upstream. This is where you
860see the value of keeping each patch (or patch series) in its own branch. It
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]861means that the patches can be moved into the "release" tree in any order.</p><div class="literallayout"><p>$ git checkout release &amp;&amp; git pull . speed-up-spinlocks</p></div><p>After a while, you will have a number of branches, and despite the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]862well chosen names you picked for each of them, you may forget what
863they are for, or what status they are in. To get a reminder of what
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]864changes are in a specific branch, use:</p><div class="literallayout"><p>$ git log linux..branchname | git shortlog</p></div><p>To see whether it has already been merged into the test or release branches,
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]865use:</p><div class="literallayout"><p>$ git log test..branchname</p></div><p>or</p><div class="literallayout"><p>$ git log release..branchname</p></div><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]866If it has been merged, then there will be no output.)</p><p>Once a patch completes the great cycle (moving from test to release,
867then pulled by Linus, and finally coming back into your local
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]868"origin/master" branch), the branch for this change is no longer needed.
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]869You detect this when the output from:</p><div class="literallayout"><p>$ git log origin..branchname</p></div><p>is empty. At this point the branch can be deleted:</p><div class="literallayout"><p>$ git branch -d branchname</p></div><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]870branch and then merge into each of the test and release branches. For
871these changes, just apply directly to the "release" branch, and then
872merge that into the "test" branch.</p><p>To create diffstat and shortlog summaries of changes to include in a "please
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]873pull" request to Linus you can use:</p><div class="literallayout"><p>$ git diff --stat origin..release</p></div><p>and</p><div class="literallayout"><p>$ git log -p origin..release | git shortlog</p></div><p>Here are some of the scripts that simplify all this even further.</p><div class="literallayout"><p>==== update script ====<br>
874# Update a branch in my GIT tree.  If the branch to be updated<br>
875# is origin, then pull from kernel.org.  Otherwise merge<br>
876# origin/master branch into test|release branch<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]877<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]878case "$1" in<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]879test|release)<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]880        git checkout $1 &amp;&amp; git pull . origin<br>
881        ;;<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]882origin)<br>
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]883        before=$(git rev-parse refs/remotes/origin/master)<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]884        git fetch origin<br>
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]885        after=$(git rev-parse refs/remotes/origin/master)<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]886        if [ $before != $after ]<br>
887        then<br>
888                git log $before..$after | git shortlog<br>
889        fi<br>
890        ;;<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]891*)<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]892        echo "Usage: $0 origin|test|release" 1&gt;&amp;2<br>
893        exit 1<br>
894        ;;<br>
895esac</p></div><div class="literallayout"><p>==== merge script ====<br>
896# Merge a branch into either the test or release branch<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]897<br>
898pname=$0<br>
899<br>
900usage()<br>
901{<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]902        echo "Usage: $pname branch test|release" 1&gt;&amp;2<br>
903        exit 1<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]904}<br>
905<br>
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]906git show-ref -q --verify -- refs/heads/"$1" || {<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]907        echo "Can't see branch &lt;$1&gt;" 1&gt;&amp;2<br>
908        usage<br>
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]909}<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]910<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]911case "$2" in<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]912test|release)<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]913        if [ $(git log $2..$1 | wc -c) -eq 0 ]<br>
914        then<br>
915                echo $1 already merged into $2 1&gt;&amp;2<br>
916                exit 1<br>
917        fi<br>
918        git checkout $2 &amp;&amp; git pull . $1<br>
919        ;;<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]920*)<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]921        usage<br>
922        ;;<br>
923esac</p></div><div class="literallayout"><p>==== status script ====<br>
924# report on status of my ia64 GIT tree<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]925<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]926gb=$(tput setab 2)<br>
927rb=$(tput setab 1)<br>
928restore=$(tput setab 9)<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]929<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]930if [ `git rev-list test..release | wc -c` -gt 0 ]<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]931then<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]932        echo $rb Warning: commits in release that are not in test $restore<br>
933        git log test..release<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]934fi<br>
935<br>
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]936for branch in `git show-ref --heads | sed 's|^.*/||'`<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]937do<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]938        if [ $branch = test -o $branch = release ]<br>
939        then<br>
940                continue<br>
941        fi<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]942<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]943        echo -n $gb ======= $branch ====== $restore " "<br>
944        status=<br>
945        for ref in test release origin/master<br>
946        do<br>
947                if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]<br>
948                then<br>
949                        status=$status${ref:0:1}<br>
950                fi<br>
951        done<br>
952        case $status in<br>
953        trl)<br>
954                echo $rb Need to pull into test $restore<br>
955                ;;<br>
956        rl)<br>
957                echo "In test"<br>
958                ;;<br>
959        l)<br>
960                echo "Waiting for linus"<br>
961                ;;<br>
962        "")<br>
963                echo $rb All done $restore<br>
964                ;;<br>
965        *)<br>
966                echo $rb "&lt;$status&gt;" $restore<br>
967                ;;<br>
968        esac<br>
969        git log origin/master..$branch | git shortlog<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]970done</p></div></div></div></div><div class="chapter" lang="en"><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="#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]971replaced. Git is designed with this assumption, and violating it will
972cause 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 Hamano3d30fd52007-05-08 00:32:53[diff] [blame]973assumption.</p><div class="section" lang="en"><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]974complicated feature, and to present it to the other developers in a way
975that makes it easy for them to read your changes, verify that they are
976correct, 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]977may 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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]978mistakes, 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 type="1"><li>
979Each patch can be applied in order.
980</li><li>
981Each patch includes a single logical change, together with a
982 message explaining the change.
983</li><li>
984No patch introduces a regression: after applying any initial
985 part of the series, the resulting project still compiles and
986 works, and has no bugs that it didn't have before.
987</li><li>
988The complete series produces the same end result as your own
989 (probably much messier!) development process did.
990</li></ol></div><p>We will introduce some tools that can help you do this, explain how to
991use them, and then explain some of the problems that can arise because
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]992you are rewriting history.</p></div><div class="section" lang="en"><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 "mywork" on a remote-tracking branch
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]993"origin", and create some commits on top of it:</p><div class="literallayout"><p>$ git checkout -b mywork origin<br>
994$ vi file.txt<br>
995$ git commit<br>
996$ vi otherfile.txt<br>
997$ git commit<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]998...</p></div><p>You have performed no merges into mywork, so it is just a simple linear
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]999sequence of patches on top of "origin":</p><pre class="literallayout"> o--o--o &lt;-- origin
1000 \
1001 o--o--o &lt;-- mywork</pre><p>Some more interesting work has been done in the upstream project, and
1002"origin" has advanced:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1003 \
1004 a--b--c &lt;-- mywork</pre><p>At this point, you could use "pull" to merge your changes back in;
1005the result would create a new merge commit, like this:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1006 \ \
1007 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]1008commits without any merges, you may instead choose to use
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1009<a class="ulink" href="git-rebase.html" target="_top">git-rebase(1)</a>:</p><div class="literallayout"><p>$ git checkout mywork<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1010$ git rebase origin</p></div><p>This will remove each of your commits from mywork, temporarily saving
Junio C Hamano0868a302008-07-22 09:20:44[diff] [blame]1011them as patches (in a directory named ".git/rebase-apply"), update mywork to
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1012point at the latest version of origin, then apply each of the saved
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1013patches to the new mywork. The result will look like:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1014 \
1015 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]1016and 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]1017to update the index with those contents, and then, instead of
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1018running <code class="literal">git commit</code>, just run</p><div class="literallayout"><p>$ git rebase --continue</p></div><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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1019return mywork to the state it had before you started the rebase:</p><div class="literallayout"><p>$ git rebase --abort</p></div></div><div class="section" lang="en"><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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]1020most recent commit using</p><div class="literallayout"><p>$ git commit --amend</p></div><p>which will replace the old commit by a new commit incorporating your
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1021changes, giving you a chance to edit the old commit message first.</p><p>You can also use a combination of this and <a class="ulink" href="git-rebase.html" target="_top">git-rebase(1)</a> to
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1022replace a commit further back in your history and recreate the
1023intervening changes on top of it. First, tag the problematic commit
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1024with</p><div class="literallayout"><p>$ git tag bad mywork~5</p></div><p>(Either gitk or <code class="literal">git log</code> may be useful for finding the commit.)</p><p>Then check out that commit, edit it, and rebase the rest of the series
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]1025on top of it (note that we could check out the commit on a temporary
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1026branch, but instead we're using a <a class="link" href="#detached-head" title="Examining an old version without creating a new branch">detached head</a>):</p><div class="literallayout"><p>$ git checkout bad<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1027$ # make changes here and update the index<br>
1028$ git commit --amend<br>
1029$ git rebase --onto HEAD bad mywork</p></div><p>When you're done, you'll be left with mywork checked out, with the top
Junio C Hamano0e3cb532007-04-17 08:28:11[diff] [blame]1030patches on mywork reapplied on top of your modified commit. You can
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1031then clean up with</p><div class="literallayout"><p>$ git tag -d bad</p></div><p>Note that the immutable nature of git history means that you haven't really
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]1032"modified" existing commits; instead, you have replaced the old commits with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1033new commits having new object names.</p></div><div class="section" lang="en"><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>Given one existing commit, the <a class="ulink" href="git-cherry-pick.html" target="_top">git-cherry-pick(1)</a> command
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1034allows you to apply the change introduced by that commit and create a
1035new commit that records it. So, for example, if "mywork" points to a
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1036series of patches on top of "origin", you might do something like:</p><div class="literallayout"><p>$ git checkout -b mywork-new origin<br>
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1037$ gitk origin..mywork &amp;</p></div><p>and browse through the list of patches in the mywork branch using gitk,
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1038applying them (possibly in a different order) to mywork-new using
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1039cherry-pick, and possibly modifying them as you go using <code class="literal">git commit —amend</code>.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1040The <a class="ulink" href="git-gui.html" target="_top">git-gui(1)</a> command may also help as it allows you to
Junio C Hamano8b8b0f22007-08-26 22:10:26[diff] [blame]1041individually select diff hunks for inclusion in the index (by
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1042right-clicking on the diff hunk and choosing "Stage Hunk for Commit").</p><p>Another technique is to use <code class="literal">git format-patch</code> to create a series of
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1043patches, then reset the state to before the patches:</p><div class="literallayout"><p>$ git format-patch origin<br>
1044$ git reset --hard origin</p></div><p>Then modify, reorder, or eliminate patches as preferred before applying
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1045them again with <a class="ulink" href="git-am.html" target="_top">git-am(1)</a>.</p></div><div class="section" lang="en"><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]1046purpose of maintaining a patch series. These are outside of the scope of
Junio C Hamanoec87f522008-12-10 08:35:25[diff] [blame]1047this manual.</p></div><div class="section" lang="en"><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]1048with merging. Suppose somebody fetches your branch and merges it into
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1049their branch, with a result something like this:</p><pre class="literallayout"> o--o--O--o--o--o &lt;-- origin
1050 \ \
1051 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
1052 /
1053 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
1054look like:</p><pre class="literallayout"> o--o--o &lt;-- new head of origin
1055 /
1056 o--o--O--o--o--o &lt;-- old head of origin
1057 \ \
1058 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]1059the old head; it treats this situation exactly the same as it would if
1060two developers had independently done the work on the old and new heads
1061in parallel. At this point, if someone attempts to merge the new head
1062in to their branch, git will attempt to merge together the two (old and
1063new) lines of development, instead of trying to replace the old by the
1064new. The results are likely to be unexpected.</p><p>You may still choose to publish branches whose history is rewritten,
1065and it may be useful for others to be able to fetch those branches in
1066order to examine or test them, but they should not attempt to pull such
1067branches into their own work.</p><p>For true distributed development that supports proper merging,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1068published branches should never be rewritten.</p></div><div class="section" lang="en"><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]1069includes merge commits. However, when the commit that it finds is a
1070merge commit, the user may need to work harder than usual to figure out
1071why that commit introduced a problem.</p><p>Imagine this history:</p><pre class="literallayout"> ---Z---o---X---...---o---A---C---D
1072 \ /
1073 o---o---Y---...---o---B</pre><p>Suppose that on the upper line of development, the meaning of one
1074of the functions that exists at Z is changed at commit X. The
1075commits from Z leading to A change both the function's
1076implementation and all calling sites that exist at Z, as well
1077as new calling sites they add, to be consistent. There is no
1078bug at A.</p><p>Suppose that in the meantime on the lower line of development somebody
1079adds a new calling site for that function at commit Y. The
1080commits from Z leading to B all assume the old semantics of that
1081function and the callers and the callee are consistent with each
1082other. There is no bug at B, either.</p><p>Suppose further that the two development lines merge cleanly at C,
1083so no conflict resolution is required.</p><p>Nevertheless, the code at C is broken, because the callers added
1084on the lower line of development have not been converted to the new
1085semantics introduced on the upper line of development. So if all
1086you know is that D is bad, that Z is good, and that
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1087<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]1088figure 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]1089normally be able to discover the problem by examining just that commit.
1090Developers can make this easy by breaking their changes into small
1091self-contained commits. That won't help in the case above, however,
1092because the problem isn't obvious from examination of any single
1093commit; instead, a global view of the development is required. To
1094make matters worse, the change in semantics in the problematic
1095function may be just one small part of the changes in the upper
1096line of development.</p><p>On the other hand, if instead of merging at C you had rebased the
1097history between Z to B on top of A, you would have gotten this
1098linear 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*,
1099and understanding why Y* was broken would probably be easier.</p><p>Partly for this reason, many experienced git users, even when
1100working on an otherwise merge-heavy project, keep the history
1101linear by rebasing against the latest upstream version before
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1102publishing.</p></div></div><div class="chapter" lang="en"><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 branches</a></span></dt></dl></div><div class="section" lang="en"><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]1103to update one branch at a time, and to store it locally under an
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1104arbitrary name:</p><div class="literallayout"><p>$ git fetch origin todo:my-todo-work</p></div><p>The first argument, "origin", just tells git to fetch from the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1105repository you originally cloned from. The second argument tells git
1106to fetch the branch named "todo" from the remote repository, and to
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1107store it locally under the name refs/heads/my-todo-work.</p><p>You can also fetch branches from other repositories; so</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git master:example-master</p></div><p>will create a new branch named "example-master" and store in it the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1108branch named "master" from the repository at the given URL. If you
1109already have a branch named example-master, it will attempt to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1110<a class="link" href="#fast-forwards" title="Fast-forward merges">fast-forward</a> to the commit given by example.com's
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1111master branch. In more detail:</p></div><div class="section" lang="en"><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, "git fetch"
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1112checks to make sure that the most recent commit on the remote
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1113branch is a descendant of the most recent commit on your copy of the
1114branch before updating your copy of the branch to point at the new
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1115commit. 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]1116 \
1117 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]1118a descendant of the old head. For example, the developer may have
1119realized she made a serious mistake, and decided to backtrack,
Junio C Hamanoc51fede2007-03-12 07:29:20[diff] [blame]1120resulting in a situation like:</p><pre class="literallayout"> o--o--o--o--a--b &lt;-- old head of the branch
1121 \
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1122 o--o--o &lt;-- new head of the branch</pre><p>In this case, "git fetch" 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]1123described in the following section. However, note that in the
1124situation above this may mean losing the commits labeled "a" and "b",
1125unless you've already created a reference of your own pointing to
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1126them.</p></div><div class="section" lang="en"><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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]1127descendant of the old head, you may force the update with:</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git +master:refs/remotes/example/master</p></div><p>Note the addition of the "+" sign. Alternatively, you can use the "-f"
1128flag to force updates of all the fetched branches, as in:</p><div class="literallayout"><p>$ git fetch -f origin</p></div><p>Be aware that commits that the old version of example/master pointed at
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]1129may be lost, as we saw in the previous section.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="remote-branch-configuration"></a>Configuring remote branches</h2></div></div></div><p>We saw above that "origin" is just a shortcut to refer to the
Junio C Hamanodb911ee2007-02-28 08:13:52[diff] [blame]1130repository that you originally cloned from. This information is
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1131stored in git configuration variables, which you can see using
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1132<a class="ulink" href="git-config.html" target="_top">git-config(1)</a>:</p><div class="literallayout"><p>$ git config -l<br>
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1133core.repositoryformatversion=0<br>
1134core.filemode=true<br>
1135core.logallrefupdates=true<br>
1136remote.origin.url=git://git.kernel.org/pub/scm/git/git.git<br>
1137remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*<br>
1138branch.master.remote=origin<br>
1139branch.master.merge=refs/heads/master</p></div><p>If there are other repositories that you also use frequently, you can
1140create similar configuration options to save typing; for example,
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1141after</p><div class="literallayout"><p>$ git config remote.example.url git://example.com/proj.git</p></div><p>then the following two commands will do the same thing:</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git master:refs/remotes/example/master<br>
1142$ git fetch example master:refs/remotes/example/master</p></div><p>Even better, if you add one more option:</p><div class="literallayout"><p>$ git config remote.example.fetch master:refs/remotes/example/master</p></div><p>then the following commands will all do the same thing:</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git master:refs/remotes/example/master<br>
1143$ git fetch example master:refs/remotes/example/master<br>
Junio C Hamano1d368882008-08-11 22:03:10[diff] [blame]1144$ git fetch example</p></div><p>You can also add a "+" to force the update each time:</p><div class="literallayout"><p>$ git config remote.example.fetch +master:ref/remotes/example/master</p></div><p>Don't do this unless you're sure you won't mind "git fetch" possibly
1145throwing away commits on <span class="emphasis"><em>example/master</em></span>.</p><p>Also note that all of the above configuration can be performed by
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1146directly editing the file .git/config instead of using
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1147<a class="ulink" href="git-config.html" target="_top">git-config(1)</a>.</p><p>See <a class="ulink" href="git-config.html" target="_top">git-config(1)</a> for more details on the configuration
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1148options mentioned above.</p></div></div><div class="chapter" lang="en"><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]1149is possible to get things done without understanding them, you will find
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1150git 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" lang="en"><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]1151under a 40-digit "object name". In fact, all the information needed to
1152represent the history of a project is stored in objects with such names.
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1153In each case the name is calculated by taking the SHA-1 hash of the
1154contents of the object. The SHA-1 hash is a cryptographic hash function.
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1155What that means to us is that it is impossible to find two different
1156objects with the same name. This has a number of advantages; among
1157others:</p><div class="itemizedlist"><ul type="disc"><li>
1158Git can quickly determine whether two objects are identical or not,
1159 just by comparing names.
1160</li><li>
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1161Since object names are computed the same way in every repository, the
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1162 same content stored in two repositories will always be stored under
1163 the same name.
1164</li><li>
1165Git can detect errors when it reads an object, by checking that the
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1166 object's name is still the SHA-1 hash of its contents.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1167</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]1168SHA-1 calculation.)</p><p>There are four different types of objects: "blob", "tree", "commit", and
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1169"tag".</p><div class="itemizedlist"><ul type="disc"><li>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1170A <a class="link" href="#def_blob_object">"blob" object</a> is used to store file data.
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1171</li><li>
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]1172A <a class="link" href="#def_tree_object">"tree" object</a> ties one or more
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1173 "blob" objects into a directory structure. In addition, a tree object
1174 can refer to other tree objects, thus creating a directory hierarchy.
1175</li><li>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1176A <a class="link" href="#def_commit_object">"commit" object</a> ties such directory hierarchies
1177 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]1178 commit contains the object name of exactly one tree designating the
1179 directory hierarchy at the time of the commit. In addition, a commit
1180 refers to "parent" commit objects that describe the history of how we
1181 arrived at that directory hierarchy.
1182</li><li>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1183A <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]1184 used to sign other objects. It contains the object name and type of
1185 another object, a symbolic name (of course!) and, optionally, a
1186 signature.
1187</li></ul></div><p>The object types in some more detail:</p><div class="section" lang="en"><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
1188of how we got there and why. Use the —pretty=raw option to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1189<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 Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1190commit:</p><div class="literallayout"><p>$ git show -s --pretty=raw 2be7fcb476<br>
1191commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4<br>
1192tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf<br>
1193parent 257a84d9d02e90447b149af58b271c19405edb6a<br>
1194author Dave Watson &lt;dwatson@mimvista.com&gt; 1187576872 -0400<br>
1195committer Junio C Hamano &lt;gitster@pobox.com&gt; 1187591163 -0700<br>
1196<br>
1197    Fix misspelling of 'suppress' in docs<br>
1198<br>
1199    Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;</p></div><p>As you can see, a commit is defined by:</p><div class="itemizedlist"><ul type="disc"><li>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1200a tree: The SHA-1 name of a tree object (as defined below), representing
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1201 the contents of a directory at a certain point in time.
1202</li><li>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1203parent(s): The SHA-1 name of some number of commits which represent the
Junio C Hamano878cc1e2007-12-14 08:35:13[diff] [blame]1204 immediately previous step(s) in the history of the project. The
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1205 example above has one parent; merge commits may have more than
1206 one. A commit with no parents is called a "root" commit, and
1207 represents the initial revision of a project. Each project must have
1208 at least one root. A project can also have multiple roots, though
1209 that isn't common (or necessarily a good idea).
1210</li><li>
1211an author: The name of the person responsible for this change, together
1212 with its date.
1213</li><li>
1214a committer: The name of the person who actually created the commit,
1215 with the date it was done. This may be different from the author, for
1216 example, if the author was someone who wrote a patch and emailed it
1217 to the person who used it to create the commit.
1218</li><li>
1219a comment describing this commit.
1220</li></ul></div><p>Note that a commit does not itself contain any information about what
1221actually changed; all changes are calculated by comparing the contents
1222of the tree referred to by this commit with the trees associated with
1223its parents. In particular, git does not attempt to record file renames
1224explicitly, though it can identify cases where the existence of the same
1225file data at changing paths suggests a rename. (See, for example, the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1226-M 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]1227commit whose parent is normally the current HEAD, and whose tree is
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1228taken from the content currently stored in the index.</p></div><div class="section" lang="en"><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
1229examine tree objects, but <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a> will give you more
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1230details:</p><div class="literallayout"><p>$ git ls-tree fb3a8bdd0ce<br>
1231100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c    .gitignore<br>
1232100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d    .mailmap<br>
1233100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3    COPYING<br>
1234040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745    Documentation<br>
1235100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200    GIT-VERSION-GEN<br>
1236100644 blob 289b046a443c0647624607d471289b2c7dcd470b    INSTALL<br>
1237100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1    Makefile<br>
1238100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52    README<br>
1239...</p></div><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]1240mode, object type, SHA-1 name, and name, sorted by name. It represents
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1241the contents of a single directory tree.</p><p>The object type may be a blob, representing the contents of a file, or
1242another tree, representing the contents of a subdirectory. Since trees
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1243and blobs, like all other objects, are named by the SHA-1 hash of their
1244contents, two trees have the same SHA-1 name if and only if their
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1245contents (including, recursively, the contents of all subdirectories)
1246are identical. This allows git to quickly determine the differences
1247between two related tree objects, since it can ignore any entries with
1248identical object names.</p><p>(Note: in the presence of submodules, trees may also have commits as
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1249entries. 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
1250attention to the executable bit.</p></div><div class="section" lang="en"><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 Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1251for example, the blob in the entry for "COPYING" from the tree above:</p><div class="literallayout"><p>$ git show 6ff87c4664<br>
1252<br>
1253 Note that the only valid version of the GPL as far as this project<br>
1254 is concerned is _this_ particular version of the license (ie v2, not<br>
1255 v2.2 or v3.x or whatever), unless explicitly otherwise stated.<br>
1256...</p></div><p>A "blob" object is nothing but a binary blob of data. It doesn't refer
1257to anything else or have attributes of any kind.</p><p>Since the blob is entirely defined by its data, if two files in a
1258directory tree (or in multiple different versions of the repository)
1259have the same contents, they will share the same blob object. The object
1260is totally independent of its location in the directory tree, and
1261renaming 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]1262<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]1263sometimes be useful for browsing the contents of a tree that is not
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1264currently checked out.</p></div><div class="section" lang="en"><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]1265from another (possibly untrusted) source, you can still trust that those
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1266contents are correct as long as the SHA-1 name agrees. This is because
1267the SHA-1 is designed so that it is infeasible to find different contents
1268that 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]1269to trust the contents of the entire directory that it refers to, and if
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1270you receive the SHA-1 name of a commit from a trusted source, then you
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1271can easily verify the entire history of commits reachable through
1272parents of that commit, and all of those contents of the trees referred
1273to 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]1274to do is to digitally sign just <span class="emphasis"><em>one</em></span> special note, which includes the
1275name of a top-level commit. Your digital signature shows others
1276that you trust that commit, and the immutability of the history of
1277commits 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]1278sending out a single email that tells the people the name (SHA-1 hash)
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1279of the top commit, and digitally sign that email using something
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1280like GPG/PGP.</p><p>To assist in this, git also provides the tag object…</p></div><div class="section" lang="en"><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
1281person ("tagger") who created the tag, and a message, which may contain
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]1282a signature, as can be seen using <a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a>:</p><div class="literallayout"><p>$ git cat-file tag v1.5.0<br>
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1283object 437b1b20df4b356c9342dac8d38849f24ef44f27<br>
1284type commit<br>
1285tag v1.5.0<br>
1286tagger Junio C Hamano &lt;junkio@cox.net&gt; 1171411200 +0000<br>
1287<br>
1288GIT 1.5.0<br>
1289-----BEGIN PGP SIGNATURE-----<br>
1290Version: GnuPG v1.4.6 (GNU/Linux)<br>
1291<br>
1292iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui<br>
1293nLE/L9aUXdWeTFPron96DLA=<br>
1294=2E+0<br>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1295-----END PGP SIGNATURE-----</p></div><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
1296objects. (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]1297"lightweight tags", which are not tag objects at all, but just simple
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1298references whose names begin with "refs/tags/").</p></div><div class="section" lang="en"><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
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1299object's SHA-1 hash (stored in .git/objects).</p><p>Unfortunately this system becomes inefficient once a project has a
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1300lot of objects. Try this on an old project:</p><div class="literallayout"><p>$ git count-objects<br>
13016930 objects, 47620 kilobytes</p></div><p>The first number is the number of objects which are kept in
1302individual files. The second is the amount of space taken up by
1303those "loose" objects.</p><p>You can save space and make git faster by moving these loose objects in
1304to a "pack file", which stores a group of objects in an efficient
1305compressed format; the details of how pack files are formatted can be
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1306found in <a class="ulink" href="technical/pack-format.txt" target="_top">technical/pack-format.txt</a>.</p><p>To put the loose objects into a pack, just run git repack:</p><div class="literallayout"><p>$ git repack<br>
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1307Generating pack...<br>
1308Done counting 6020 objects.<br>
1309Deltifying 6020 objects.<br>
1310 100% (6020/6020) done<br>
1311Writing 6020 objects.<br>
1312 100% (6020/6020) done<br>
1313Total 6020, written 6020 (delta 4070), reused 0 (delta 0)<br>
1314Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.</p></div><p>You can then run</p><div class="literallayout"><p>$ git prune</p></div><p>to remove any of the "loose" objects that are now contained in the
1315pack. This will also remove any unreferenced objects (which may be
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1316created when, for example, you use "git reset" to remove a commit).
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1317You can verify that the loose objects are gone by looking at the
1318.git/objects directory or by running</p><div class="literallayout"><p>$ git count-objects<br>
13190 objects, 0 kilobytes</p></div><p>Although the object files are gone, any commands that refer to those
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1320objects 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
1321you, so is normally the only high-level command you need.</p></div><div class="section" lang="en"><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 Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1322objects. They are not a problem.</p><p>The most common cause of dangling objects is that you've rebased a
1323branch, or you have pulled from somebody else who rebased a branch—see
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1324<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]1325branch still exists, as does everything it pointed to. The branch
1326pointer 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 Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1327example, a "dangling blob" may arise because you did a "git add" of a
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1328file, but then, before you actually committed it and made it part of the
1329bigger picture, you changed something else in that file and committed
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1330that <span class="strong"><strong>updated</strong></span> thing—the old state that you added originally ends up
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1331not being pointed to by any commit or tree, so it's now a dangling blob
1332object.</p><p>Similarly, when the "recursive" merge strategy runs, and finds that
1333there are criss-cross merges and thus more than one merge base (which is
1334fairly unusual, but it does happen), it will generate one temporary
1335midway tree (or possibly even more, if you had lots of criss-crossing
1336merges and more than two merge bases) as a temporary internal merge
1337base, and again, those are real objects, but the end result will not end
1338up pointing to them, so they end up "dangling" in your repository.</p><p>Generally, dangling objects aren't anything to worry about. They can
1339even be very useful: if you screw something up, the dangling objects can
1340be how you recover your old tree (say, you did a rebase, and realized
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1341that you really didn't want to—you can look at what dangling objects
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1342you have, and decide to reset your head to some old dangling state).</p><p>For commits, you can just use:</p><div class="literallayout"><p>$ gitk &lt;dangling-commit-sha-goes-here&gt; --not --all</p></div><p>This asks for all the history reachable from the given commit but not
1343from any branch, tag, or other reference. If you decide it's something
1344you want, you can always create a new reference to it, e.g.,</p><div class="literallayout"><p>$ git branch recovered-branch &lt;dangling-commit-sha-goes-here&gt;</p></div><p>For blobs and trees, you can't do the same, but you can still examine
1345them. You can just do</p><div class="literallayout"><p>$ git show &lt;dangling-blob/tree-sha-goes-here&gt;</p></div><p>to show what the contents of the blob were (or, for a tree, basically
1346what the "ls" for that directory was), and that may give you some idea
1347of what the operation was that left that dangling object.</p><p>Usually, dangling blobs and trees aren't very interesting. They're
1348almost always the result of either being a half-way mergebase (the blob
1349will often even have the conflict markers from a merge in it, if you
1350have had conflicting merges that you fixed up by hand), or simply
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1351because you interrupted a "git fetch" with ^C or something like that,
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1352leaving _some_ of the new objects in the object database, but just
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1353dangling and useless.</p><p>Anyway, once you are sure that you're not interested in any dangling
1354state, you can just prune all unreachable objects:</p><div class="literallayout"><p>$ git prune</p></div><p>and they'll be gone. But you should only run "git prune" on a quiescent
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1355repository—it's kind of like doing a filesystem fsck recovery: you
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1356don't want to do that while the filesystem is mounted.</p><p>(The same is true of "git fsck" itself, btw, but since
1357<code class="literal">git fsck</code> never actually <span class="strong"><strong>changes</strong></span> the repository, it just reports
1358on what it found, <code class="literal">git fsck</code> itself is never <span class="emphasis"><em>dangerous</em></span> to run.
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1359Running it while somebody is actually changing the repository can cause
1360confusing and scary messages, but it won't actually do anything bad. In
1361contrast, running "git prune" while somebody is actively changing the
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1362repository is a <span class="strong"><strong>BAD</strong></span> idea).</p></div><div class="section" lang="en"><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
1363the absence of bugs in git itself, it is still possible that hardware or
1364operating system errors could corrupt data.</p><p>The first defense against such problems is backups. You can back up a
1365git directory using clone, or just using cp, tar, or any other backup
1366mechanism.</p><p>As a last resort, you can search for the corrupted objects and attempt
1367to replace them by hand. Back up your repository before attempting this
1368in 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]1369which is sometimes a solvable problem. (Recovering missing trees and
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1370especially 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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1371it 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><div class="literallayout"><p>$ git fsck --full<br>
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1372broken link from    tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8<br>
1373              to    blob 4b9458b3786228369c63936db65827de3cc06200<br>
1374missing blob 4b9458b3786228369c63936db65827de3cc06200</p></div><p>(Typically there will be some "dangling object" messages too, but they
1375aren't interesting.)</p><p>Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6
1376points to it. If you could find just one copy of that missing blob
1377object, possibly in some other repository, you could move it into
1378.git/objects/4b/9458b3… and be done. Suppose you can't. You can
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1379still 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 Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1380which might output something like:</p><div class="literallayout"><p>$ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8<br>
1381100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8    .gitignore<br>
1382100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883    .mailmap<br>
1383100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c    COPYING<br>
1384...<br>
1385100644 blob 4b9458b3786228369c63936db65827de3cc06200    myfile<br>
1386...</p></div><p>So now you know that the missing blob was the data for a file named
1387"myfile". And chances are you can also identify the directory—let's
1388say it's in "somedirectory". If you're lucky the missing copy might be
1389the same as the copy you have checked out in your working tree at
1390"somedirectory/myfile"; you can test whether that's right with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1391<a class="ulink" href="git-hash-object.html" target="_top">git-hash-object(1)</a>:</p><div class="literallayout"><p>$ git hash-object -w somedirectory/myfile</p></div><p>which will create and store a blob object with the contents of
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1392somedirectory/myfile, and output the SHA-1 of that object. if you're
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]1393extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in
1394which case you've guessed right, and the corruption is fixed!</p><p>Otherwise, you need more information. How do you tell which version of
1395the file has been lost?</p><p>The easiest way to do this is with:</p><div class="literallayout"><p>$ git log --raw --all --full-history -- somedirectory/myfile</p></div><p>Because you're asking for raw output, you'll now get something like</p><div class="literallayout"><p>commit abc<br>
1396Author:<br>
1397Date:<br>
1398...<br>
1399:100644 100644 4b9458b... newsha... M somedirectory/myfile<br>
1400<br>
1401<br>
1402commit xyz<br>
1403Author:<br>
1404Date:<br>
1405<br>
1406...<br>
1407:100644 100644 oldsha... 4b9458b... M somedirectory/myfile</p></div><p>This tells you that the immediately preceding version of the file was
1408"newsha", and that the immediately following version was "oldsha".
1409You also know the commit messages that went with the change from oldsha
1410to 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
1411shot 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><div class="literallayout"><p>$ git hash-object -w &lt;recreated-file&gt;</p></div><p>and your repository is good again!</p><p>(Btw, you could have ignored the fsck, and started with doing a</p><div class="literallayout"><p>$ git log --raw --all</p></div><p>and just looked for the sha of the missing object (4b9458b..) in that
1412whole thing. It's up to you - git does <span class="strong"><strong>have</strong></span> a lot of information, it is
1413just missing one particular blob version.</p></div></div><div class="section" lang="en"><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 .git/index) containing a
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1414sorted list of path names, each with permissions and the SHA-1 of a blob
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1415object; <a class="ulink" href="git-ls-files.html" target="_top">git-ls-files(1)</a> can show you the contents of the index:</p><div class="literallayout"><p>$ git ls-files --stage<br>
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1416100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0       .gitignore<br>
1417100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0       .mailmap<br>
1418100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0       COPYING<br>
1419100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0       Documentation/.gitignore<br>
1420100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0       Documentation/Makefile<br>
1421...<br>
1422100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0       xdiff/xtypes.h<br>
1423100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0       xdiff/xutils.c<br>
1424100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0       xdiff/xutils.h</p></div><p>Note that in older documentation you may see the index called the
1425"current directory cache" or just the "cache". It has three important
1426properties:</p><div class="orderedlist"><ol type="1"><li><p>
1427The index contains all the information necessary to generate a single
1428(uniquely determined) tree object.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1429</p><p>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]1430from the index, stores it in the object database, and uses it as the
1431tree object associated with the new commit.</p></li><li><p>
1432The index enables fast comparisons between the tree object it defines
1433and the working tree.
1434</p><p>It does this by storing some additional data for each entry (such as
1435the last modified time). This data is not displayed above, and is not
1436stored in the created tree object, but it can be used to determine
1437quickly which files in the working directory differ from what was
1438stored in the index, and thus save git from having to read all of the
1439data from such files to look for changes.</p></li><li><p>
1440It can efficiently represent information about merge conflicts
1441between different tree objects, allowing each pathname to be
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1442associated with sufficient information about the trees involved that
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1443you can create a three-way merge between them.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1444</p><p>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]1445store multiple versions of a single file (called "stages"). The third
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1446column 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]1447number, and will take on values other than 0 for files with merge
1448conflicts.</p></li></ol></div><p>The index is thus a sort of temporary staging area, which is filled with
1449a 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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1450information as long as you have the name of the tree that it described.</p></div></div><div class="chapter" lang="en"><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 Hamano4fd58d42007-09-30 00:51:14[diff] [blame]1451example, an embedded Linux distribution's source tree would include every
1452piece of software in the distribution with some local modifications; a movie
1453player might need to build against a specific, known-working version of a
1454decompression library; several independent programs might all share the same
1455build scripts.</p><p>With centralized revision control systems this is often accomplished by
1456including every module in one single repository. Developers can check out
1457all modules or only the modules they need to work with. They can even modify
1458files across several modules in a single commit while moving things around
1459or updating APIs and translations.</p><p>Git does not allow partial checkouts, so duplicating this approach in Git
1460would force developers to keep a local copy of modules they are not
1461interested in touching. Commits in an enormous checkout would be slower
1462than you'd expect as Git would have to scan every directory for changes.
1463If modules have a lot of local history, clones would take forever.</p><p>On the plus side, distributed revision control systems can much better
1464integrate with external sources. In a centralized model, a single arbitrary
1465snapshot of the external project is exported from its own revision control
1466and then imported into the local revision control on a vendor branch. All
1467the history is hidden. With distributed revision control you can clone the
1468entire external history and much more easily follow development and re-merge
1469local changes.</p><p>Git's submodule support allows a repository to contain, as a subdirectory, a
1470checkout of an external project. Submodules maintain their own identity;
1471the submodule support just stores the submodule repository location and
1472commit ID, so other developers who clone the containing project
1473("superproject") can easily clone all the submodules at the same revision.
1474Partial checkouts of the superproject are possible: you can tell Git to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1475clone 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]1476with Git 1.5.2 can look up the submodule commits in the repository and
1477manually check them out; earlier versions won't recognize the submodules at
1478all.</p><p>To see how submodule support works, create (for example) four example
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1479repositories that can be used later as a submodule:</p><div class="literallayout"><p>$ mkdir ~/git<br>
1480$ cd ~/git<br>
1481$ for i in a b c d<br>
1482do<br>
1483        mkdir $i<br>
1484        cd $i<br>
1485        git init<br>
1486        echo "module $i" &gt; $i.txt<br>
1487        git add $i.txt<br>
1488        git commit -m "Initial commit, submodule $i"<br>
1489        cd ..<br>
1490done</p></div><p>Now create the superproject and add all the submodules:</p><div class="literallayout"><p>$ mkdir super<br>
1491$ cd super<br>
1492$ git init<br>
1493$ for i in a b c d<br>
1494do<br>
Junio C Hamano7f80ae82008-07-30 18:31:35[diff] [blame]1495        git submodule add ~/git/$i $i<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1496done</p></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Do not use local URLs here if you plan to publish your superproject!</p></div><p>See what files <code class="literal">git submodule</code> created:</p><div class="literallayout"><p>$ ls -a<br>
1497.  ..  .git  .gitmodules  a  b  c  d</p></div><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 type="disc"><li>
Junio C Hamano7f80ae82008-07-30 18:31:35[diff] [blame]1498It clones the submodule from &lt;repo&gt; to the given &lt;path&gt; under the
1499 current directory and by default checks out the master branch.
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1500</li><li>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1501It 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]1502 adds this file to the index, ready to be committed.
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1503</li><li>
1504It adds the submodule's current commit ID to the index, ready to be
1505 committed.
1506</li></ul></div><p>Commit the superproject:</p><div class="literallayout"><p>$ git commit -m "Add submodules a, b, c and d."</p></div><p>Now clone the superproject:</p><div class="literallayout"><p>$ cd ..<br>
1507$ git clone super cloned<br>
1508$ cd cloned</p></div><p>The submodule directories are there, but they're empty:</p><div class="literallayout"><p>$ ls -a a<br>
1509.  ..<br>
1510$ git submodule status<br>
1511-d266b9873ad50488163457f025db7cdd9683d88b a<br>
1512-e81d457da15309b4fef4249aba9b50187999670d b<br>
1513-c1536a972b9affea0f16e0680ba87332dc059146 c<br>
1514-d96249ff5d57de5de093e6baff9e0aafa5276a74 d</p></div><div class="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
1515should match the HEAD commit object names of your repositories. You can check
1516it 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 Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1517init</code> to add the submodule repository URLs to <code class="literal">.git/config</code>:</p><div class="literallayout"><p>$ git submodule init</p></div><p>Now use <code class="literal">git submodule update</code> to clone the repositories and check out the
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1518commits specified in the superproject:</p><div class="literallayout"><p>$ git submodule update<br>
1519$ cd a<br>
1520$ ls -a<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1521.  ..  .git  a.txt</p></div><p>One major difference between <code class="literal">git submodule update</code> and <code class="literal">git submodule add</code> is
1522that <code class="literal">git submodule update</code> checks out a specific commit, rather than the tip
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1523of a branch. It's like checking out a tag: the head is detached, so you're not
1524working on a branch.</p><div class="literallayout"><p>$ git branch<br>
1525* (no branch)<br>
1526  master</p></div><p>If you want to make a change within a submodule and you have a detached head,
1527then you should create or checkout a branch, make your changes, publish the
1528change within the submodule, and then update the superproject to reference the
1529new commit:</p><div class="literallayout"><p>$ git checkout master</p></div><p>or</p><div class="literallayout"><p>$ git checkout -b fix-up</p></div><p>then</p><div class="literallayout"><p>$ echo "adding a line again" &gt;&gt; a.txt<br>
1530$ git commit -a -m "Updated the submodule from within the superproject."<br>
1531$ git push<br>
1532$ cd ..<br>
1533$ git diff<br>
1534diff --git a/a b/a<br>
1535index d266b98..261dfac 160000<br>
1536--- a/a<br>
1537+++ b/a<br>
1538@@ -1 +1 @@<br>
1539-Subproject commit d266b9873ad50488163457f025db7cdd9683d88b<br>
1540+Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24<br>
1541$ git add a<br>
1542$ git commit -m "Updated submodule a."<br>
1543$ git push</p></div><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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1544submodules, too.</p><div class="section" lang="en"><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]1545superproject that references it. If you forget to publish the submodule change,
1546others won't be able to clone the repository:</p><div class="literallayout"><p>$ cd ~/git/super/a<br>
1547$ echo i added another line to this file &gt;&gt; a.txt<br>
1548$ git commit -a -m "doing it wrong this time"<br>
1549$ cd ..<br>
1550$ git add a<br>
1551$ git commit -m "Updated submodule a again."<br>
1552$ git push<br>
1553$ cd ~/git/cloned<br>
1554$ git pull<br>
1555$ git submodule update<br>
1556error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git.<br>
1557Did you forget to 'git add'?<br>
1558Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a'</p></div><p>You also should not rewind branches in a submodule beyond commits that were
1559ever 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
1560changes within a submodule without checking out a branch first. They will be
1561silently overwritten:</p><div class="literallayout"><p>$ cat a.txt<br>
1562module a<br>
1563$ echo line added from private2 &gt;&gt; a.txt<br>
1564$ git commit -a -m "line added inside private2"<br>
1565$ cd ..<br>
1566$ git submodule update<br>
1567Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b'<br>
1568$ cd a<br>
1569$ cat a.txt<br>
1570module a</p></div><div class="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>This is not the case if you did not commit your changes.</p></div></div><div class="chapter" lang="en"><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 -&gt; index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index -&gt; object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database -&gt; index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index -&gt; 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 Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1571scripts using a smaller core of low-level git commands. These can still
1572be useful when doing unusual things with git, or just as a way to
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1573understand its inner workings.</p><div class="section" lang="en"><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,
1574though 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
1575arbitrary 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
1576accessed by <a class="ulink" href="git-ls-tree.html" target="_top">git-ls-tree(1)</a>. Two trees can be compared with
1577<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
1578verified by <a class="ulink" href="git-verify-tag.html" target="_top">git-verify-tag(1)</a>, though it is normally simpler to
1579use <a class="ulink" href="git-tag.html" target="_top">git-tag(1)</a> for both.</p></div><div class="section" lang="en"><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>,
1580<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]1581between the working tree, the index, and the object database. Git
1582provides low-level operations which perform each of these steps
1583individually.</p><p>Generally, all "git" operations work on the index file. Some operations
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1584work <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]1585index), but most operations move data between the index file and either
1586the database or the working directory. Thus there are four main
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1587combinations:</p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="working-directory-to-index"></a>working directory -&gt; 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]1588information from the working directory. You generally update the
1589index information by just specifying the filename you want to update,
1590like so:</p><div class="literallayout"><p>$ git update-index filename</p></div><p>but to avoid common mistakes with filename globbing etc, the command
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1591will not normally add totally new entries or remove old entries,
1592i.e. it will normally just update existing cache entries.</p><p>To tell git that yes, you really do realize that certain files no
1593longer exist, or that new files should be added, you
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1594should 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]1595necessarily be removed: if the files still exist in your directory
1596structure, the index will be updated with their new status, not
Junio C Hamano774239c2007-12-01 01:57:43[diff] [blame]1597removed. 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]1598considering a removed file to be a valid thing, and if the file really
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1599does 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]1600will refresh the "stat" information of each index to match the current
1601stat information. It will <span class="emphasis"><em>not</em></span> update the object status itself, and
1602it will only update the fields that are used to quickly test whether
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1603an 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
1604<a class="ulink" href="git-update-index.html" target="_top">git-update-index(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="index-to-object-database"></a>index -&gt; object database</h3></div></div></div><p>You write your current index file to a "tree" object with the program</p><div class="literallayout"><p>$ git write-tree</p></div><p>that doesn't come with any options—it will just write out the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1605current index into the set of tree objects that describe that state,
1606and it will return the name of the resulting top-level tree. You can
1607use that tree to re-generate the index at any time by going in the
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]1608other direction:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="object-database-to-index"></a>object database -&gt; index</h3></div></div></div><p>You read a "tree" file from the object database, and use that to
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1609populate (and overwrite—don't do this if your index contains any
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1610unsaved state that you might want to restore later!) your current
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1611index. Normal operation is just</p><div class="literallayout"><p>$ git read-tree &lt;SHA-1 of tree&gt;</p></div><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]1612earlier. However, that is only your <span class="emphasis"><em>index</em></span> file: your working
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]1613directory contents have not been modified.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="index-to-working-directory"></a>index -&gt; working directory</h3></div></div></div><p>You update your working directory from the index by "checking out"
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1614files. This is not a very common operation, since normally you'd just
1615keep your files updated, and rather than write to your working
1616directory, you'd tell the index files about the changes in your
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1617working 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 Hamano8f62db92007-02-01 00:22:22[diff] [blame]1618else's version, or just restore a previous tree, you'd populate your
1619index file with read-tree, and then you need to check out the result
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1620with</p><div class="literallayout"><p>$ git checkout-index filename</p></div><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]1621if you have an old version of the tree already checked out, you will
1622need to use the "-f" flag (<span class="emphasis"><em>before</em></span> the "-a" flag or the filename) to
1623<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 Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1624from one representation to the other:</p></div><div class="section" lang="en"><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 "git write-tree", you'd
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1625create a "commit" object that refers to that tree and the history
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1626behind it—most notably the "parent" commits that preceded it in
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1627history.</p><p>Normally a "commit" has one parent: the previous state of the tree
1628before a certain change was made. However, sometimes it can have two
1629or more parent commits, in which case we call it a "merge", due to the
1630fact that such a commit brings together ("merges") two or more
1631previous states represented by other commits.</p><p>In other words, while a "tree" represents a particular directory state
1632of a working directory, a "commit" represents that state in "time",
1633and explains how we got there.</p><p>You create a commit object by giving it the tree that describes the
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1634state at the time of the commit, and a list of parents:</p><div class="literallayout"><p>$ git commit-tree &lt;tree&gt; -p &lt;parent&gt; [-p &lt;parent2&gt; ..]</p></div><p>and then giving the reason for the commit on stdin (either through
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1635redirection 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]1636that commit, and you should save it away for later use. Normally,
1637you'd commit a new <code class="literal">HEAD</code> state, and while git doesn't care where you
1638save the note about that state, in practice we tend to just write the
1639result to the file pointed at by <code class="literal">.git/HEAD</code>, so that we can always see
1640what the last committed state was.</p><p>Here is an ASCII art by Jon Loeliger that illustrates how
1641various pieces fit together.</p><div class="literallayout"><p><br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1642                     commit-tree<br>
1643                      commit obj<br>
1644                       +----+<br>
1645                       |    |<br>
1646                       |    |<br>
1647                       V    V<br>
1648                    +-----------+<br>
1649                    | Object DB |<br>
1650                    |  Backing  |<br>
1651                    |   Store   |<br>
1652                    +-----------+<br>
1653                       ^<br>
1654           write-tree  |     |<br>
1655             tree obj  |     |<br>
1656                       |     |  read-tree<br>
1657                       |     |  tree obj<br>
1658                             V<br>
1659                    +-----------+<br>
1660                    |   Index   |<br>
1661                    |  "cache"  |<br>
1662                    +-----------+<br>
1663         update-index  ^<br>
1664             blob obj  |     |<br>
1665                       |     |<br>
1666    checkout-index -u  |     |  checkout-index<br>
1667             stat      |     |  blob obj<br>
1668                             V<br>
1669                    +-----------+<br>
1670                    |  Working  |<br>
1671                    | Directory |<br>
1672                    +-----------+<br>
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]1673</p></div></div></div><div class="section" lang="en"><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]1674index with various helper tools. For every object, you can use
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1675<a class="ulink" href="git-cat-file.html" target="_top">git-cat-file(1)</a> to examine details about the
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1676object:</p><div class="literallayout"><p>$ git cat-file -t &lt;objectname&gt;</p></div><p>shows the type of the object, and once you have the type (which is
1677usually implicit in where you find the object), you can use</p><div class="literallayout"><p>$ git cat-file blob|tree|commit|tag &lt;objectname&gt;</p></div><p>to show its contents. NOTE! Trees have binary content, and as a result
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1678there is a special helper for showing that content, called
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1679<code class="literal">git ls-tree</code>, which turns the binary content into a more easily
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1680readable form.</p><p>It's especially instructive to look at "commit" objects, since those
1681tend to be small and fairly self-explanatory. In particular, if you
1682follow the convention of having the top commit name in <code class="literal">.git/HEAD</code>,
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1683you can do</p><div class="literallayout"><p>$ git cat-file commit HEAD</p></div><p>to see what the top commit was.</p></div><div class="section" lang="en"><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 helps you do a three-way merge, which you can expand to n-way by
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1684repeating the merge procedure arbitrary times until you finally
1685"commit" the state. The normal situation is that you'd only do one
1686three-way merge (two parents), and commit it, but if you like to, you
1687can do multiple parents in one go.</p><p>To do a three-way merge, you need the two sets of "commit" objects
1688that you want to merge, use those to find the closest common parent (a
1689third "commit" object), and then use those commit objects to find the
1690state of the directory ("tree" object) at these points.</p><p>To get the "base" for the merge, you first look up the common parent
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1691of two commits with</p><div class="literallayout"><p>$ git merge-base &lt;commit1&gt; &lt;commit2&gt;</p></div><p>which will return you the commit they are both based on. You should
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1692now look up the "tree" objects of those commits, which you can easily
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1693do with (for example)</p><div class="literallayout"><p>$ git cat-file commit &lt;commitname&gt; | head -1</p></div><p>since the tree object information is always the first line in a commit
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1694object.</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]1695tree, aka the common tree, and the two "result" trees, aka the branches
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1696you want to merge), you do a "merge" read into the index. This will
1697complain if it has to throw away your old index contents, so you should
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1698make sure that you've committed those—in fact you would normally
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1699always do a merge against your last commit (which should thus match what
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1700you have in your current index anyway).</p><p>To do the merge, do</p><div class="literallayout"><p>$ git read-tree -m -u &lt;origtree&gt; &lt;yourtree&gt; &lt;targettree&gt;</p></div><p>which will do all trivial merge operations for you directly in the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1701index file, and you can just write the result out with
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1702<code class="literal">git write-tree</code>.</p></div><div class="section" lang="en"><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]1703been added, moved or removed, or if both branches have modified the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1704same file, you will be left with an index tree that contains "merge
1705entries" in it. Such an index tree can <span class="emphasis"><em>NOT</em></span> be written out to a tree
1706object, and you will have to resolve any such merge clashes using
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1707other 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>
1708command. An example:</p><div class="literallayout"><p>$ git read-tree -m $orig HEAD $target<br>
1709$ git ls-files --unmerged<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1710100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1       hello.c<br>
1711100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2       hello.c<br>
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1712100644 cc44c73eb783565da5831b4d820c962954019b69 3       hello.c</p></div><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]1713the blob mode bits, blob SHA-1, <span class="emphasis"><em>stage number</em></span>, and the
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1714filename. The <span class="emphasis"><em>stage number</em></span> is git's way to say which tree it
1715came from: stage 1 corresponds to <code class="literal">$orig</code> tree, stage 2 <code class="literal">HEAD</code>
1716tree, and stage3 <code class="literal">$target</code> tree.</p><p>Earlier we said that trivial merges are done inside
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1717<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]1718from <code class="literal">$orig</code> to <code class="literal">HEAD</code> nor <code class="literal">$target</code>, or if the file changed
1719from <code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> the same way,
1720obviously the final outcome is what is in <code class="literal">HEAD</code>. What the
1721above example shows is that file <code class="literal">hello.c</code> was changed from
1722<code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> in a different way.
1723You could resolve this by running your favorite 3-way merge
Junio C Hamano3d30fd52007-05-08 00:32:53[diff] [blame]1724program, e.g. <code class="literal">diff3</code>, <code class="literal">merge</code>, or git's own merge-file, on
Junio C Hamanofce7c7e2008-07-02 03:06:38[diff] [blame]1725the blob objects from these three stages yourself, like this:</p><div class="literallayout"><p>$ git cat-file blob 263414f... &gt;hello.c~1<br>
1726$ git cat-file blob 06fa6a2... &gt;hello.c~2<br>
1727$ git cat-file blob cc44c73... &gt;hello.c~3<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1728$ git merge-file hello.c~2 hello.c~1 hello.c~3</p></div><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]1729with conflict markers if there are conflicts. After verifying
1730the merge result makes sense, you can tell git what the final
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1731merge result for this file is by:</p><div class="literallayout"><p>$ mv -f hello.c~2 hello.c<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1732$ git update-index hello.c</p></div><p>When a path is in the "unmerged" state, running <code class="literal">git update-index</code> for
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1733that path tells git to mark the path resolved.</p><p>The above is the description of a git merge at the lowest level,
1734to help you understand what conceptually happens under the hood.
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1735In practice, nobody, not even git itself, runs <code class="literal">git cat-file</code> three times
1736for this. There is a <code class="literal">git merge-index</code> program that extracts the
1737stages to temporary files and calls a "merge" script on it:</p><div class="literallayout"><p>$ git merge-index git-merge-one-file hello.c</p></div><p>and that is what higher level <code class="literal">git merge -s resolve</code> is implemented with.</p></div></div><div class="chapter" lang="en"><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
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1738probably only git developers need to understand.</p><div class="section" lang="en"><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
1739format of the object (i.e. how it is used, and how it can refer to other
1740objects). There are currently four different object types: "blob",
1741"tree", "commit", and "tag".</p><p>Regardless of object type, all objects share the following
1742characteristics: they are all deflated with zlib, and have a header
1743that not only specifies their type, but also provides size information
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1744about the data in the object. It's worth noting that the SHA-1 hash
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1745that is used to name the object is the hash of the original data
1746plus this header, so <code class="literal">sha1sum</code> <span class="emphasis"><em>file</em></span> does not match the object name
1747for <span class="emphasis"><em>file</em></span>.
1748(Historical note: in the dawn of the age of git the hash
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1749was the SHA-1 of the <span class="emphasis"><em>compressed</em></span> object.)</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]1750independently of the contents or the type of the object: all objects can
1751be validated by verifying that (a) their hashes match the content of the
1752file and (b) the object successfully inflates to a stream of bytes that
1753forms a sequence of &lt;ascii type without space&gt; + &lt;space&gt; + &lt;ascii decimal
1754size&gt; + &lt;byte\0&gt; + &lt;binary object data&gt;.</p><p>The structured objects can further have their structure and
1755connectivity to other objects verified. This is generally done with
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1756the <code class="literal">git fsck</code> program, which generates a full dependency graph
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]1757of all objects, and verifies their internal consistency (in addition
1758to just verifying their superficial consistency through the hash).</p></div><div class="section" lang="en"><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]1759source code. This section gives you a little guidance to show where to
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1760start.</p><p>A good place to start is with the contents of the initial commit, with:</p><div class="literallayout"><p>$ git checkout e83c5163</p></div><p>The initial revision lays the foundation for almost everything git has
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1761today, but is small enough to read in one sitting.</p><p>Note that terminology has changed since that revision. For example, the
1762README in that revision uses the word "changeset" to describe what we
Junio C Hamanod32738e2008-07-09 19:53:42[diff] [blame]1763now 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]1764file is still called <code class="literal">cache.h</code>. Remark: Not much reason to change it now,
1765especially since there is no good single name for it anyway, because it is
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1766basically _the_ header file which is included by _all_ 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]1767more 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
1768which were extremely simple, and which you used in scripts, piping the
1769output of one into another. This turned out to be good for initial
1770development, since it was easier to test new things. However, recently
1771many of these parts have become builtins, and some of the core has been
1772"libified", i.e. put into libgit.a for performance, portability reasons,
1773and to avoid code duplication.</p><p>By now, you know what the index is (and find the corresponding data
1774structures in <code class="literal">cache.h</code>), and that there are just a couple of object types
1775(blobs, trees, commits and tags) which inherit their common structure from
1776<code class="literal">struct object</code>, which is their first member (and thus, you can cast e.g.
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1777<code class="literal">(struct object *)commit</code> to achieve the _same_ as <code class="literal">&amp;commit-&gt;object</code>, i.e.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1778get 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]1779There are quite a few ways to name an object (and not only revisions!).
1780All of these are handled in <code class="literal">sha1_name.c</code>. Just have a quick look at
1781the function <code class="literal">get_sha1()</code>. A lot of the special handling is done by
1782functions 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 Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1783the revision walker.</p><p>Basically, the initial version of <code class="literal">git log</code> was a shell script:</p><div class="literallayout"><p>$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \<br>
1784        LESS=-S ${PAGER:-less}</p></div><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 Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1785_always_ printed a list of revisions to stdout. It is still functional,
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1786and needs to, since most new Git programs start out as scripts using
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1787<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]1788options that were relevant for the different plumbing commands that were
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1789called 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]1790<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]1791controls 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]1792<code class="literal">setup_revisions()</code>, which parses the revisions and the common command line
1793options for the revision walker. This information is stored in the struct
1794<code class="literal">rev_info</code> for later consumption. You can do your own command line option
1795parsing after calling <code class="literal">setup_revisions()</code>. After that, you have to call
1796<code class="literal">prepare_revision_walk()</code> for initialization, and then you can get the
1797commits 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,
1798just 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]1799<code class="literal">git show v1.3.0~155^2~4</code> and scroll down to that function (note that you
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1800no 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 _contained_ in the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1801command <code class="literal">git</code>. The source side of a builtin is</p><div class="itemizedlist"><ul type="disc"><li>
1802a function called <code class="literal">cmd_&lt;bla&gt;</code>, typically defined in <code class="literal">builtin-&lt;bla&gt;.c</code>,
1803 and declared in <code class="literal">builtin.h</code>,
1804</li><li>
1805an entry in the <code class="literal">commands[]</code> array in <code class="literal">git.c</code>, and
1806</li><li>
1807an entry in <code class="literal">BUILTIN_OBJECTS</code> in the <code class="literal">Makefile</code>.
1808</li></ul></div><p>Sometimes, more than one builtin is contained in one source file. For
1809example, <code class="literal">cmd_whatchanged()</code> and <code class="literal">cmd_log()</code> both reside in <code class="literal">builtin-log.c</code>,
1810since they share quite a bit of code. In that case, the commands which are
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1811_not_ 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]1812<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]1813but 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
1814the organization of Git (after you know the basic concepts).</p><p>So, think about something which you are interested in, say, "how can I
1815access a blob just knowing the object name of it?". The first step is to
1816find a Git command with which you can do it. In this example, it is either
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1817<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 type="disc"><li>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1818is plumbing, and
1819</li><li>
1820was around even in the initial commit (it literally went only through
1821 some 20 revisions as <code class="literal">cat-file.c</code>, was renamed to <code class="literal">builtin-cat-file.c</code>
1822 when made a builtin, and then saw less than 10 versions).
1823</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 Hamanocc13f552007-07-24 08:59:43[diff] [blame]1824it does.</p><div class="literallayout"><p>        git_config(git_default_config);<br>
1825        if (argc != 3)<br>
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]1826                usage("git cat-file [-t|-s|-e|-p|&lt;type&gt;] &lt;sha1&gt;");<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1827        if (get_sha1(argv[2], sha1))<br>
1828                die("Not a valid object name %s", argv[2]);</p></div><p>Let's skip over the obvious details; the only really interesting part
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1829here is the call to <code class="literal">get_sha1()</code>. It tries to interpret <code class="literal">argv[2]</code> as an
1830object name, and if it refers to an object which is present in the current
1831repository, 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 type="disc"><li>
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1832<code class="literal">get_sha1()</code> returns 0 on _success_. This might surprise some new
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1833 Git hackers, but there is a long tradition in UNIX to return different
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1834 negative numbers in case of different errors—and 0 on success.
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1835</li><li>
1836the variable <code class="literal">sha1</code> in the function signature of <code class="literal">get_sha1()</code> is <code class="literal">unsigned
1837 char *</code>, but is actually expected to be a pointer to <code class="literal">unsigned
1838 char[20]</code>. This variable will contain the 160-bit SHA-1 of the given
1839 commit. Note that whenever a SHA-1 is passed as <code class="literal">unsigned char *</code>, it
1840 is the binary representation, as opposed to the ASCII representation in
1841 hex characters, which is passed as <code class="literal">char *</code>.
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1842</li></ul></div><p>You will see both of these things throughout the code.</p><p>Now, for the meat:</p><div class="literallayout"><p>        case 0:<br>
1843                buf = read_object_with_reference(sha1, argv[1], &amp;size, NULL);</p></div><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]1844object). To know how the function <code class="literal">read_object_with_reference()</code> actually
1845works, find the source code for it (something like <code class="literal">git grep
1846read_object_with | grep ":[a-z]"</code> in the git repository), and read
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1847the source.</p><p>To find out how the result can be used, just read on in <code class="literal">cmd_cat_file()</code>:</p><div class="literallayout"><p>        write_or_die(1, buf, size);</p></div><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]1848it helps to search through the output of <code class="literal">git log</code>, and then <code class="literal">git show</code> the
1849corresponding commit.</p><p>Example: If you know that there was some test case for <code class="literal">git bundle</code>, but
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]1850do not remember where it was (yes, you _could_ <code class="literal">git grep bundle t/</code>, but that
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]1851does not illustrate the point!):</p><div class="literallayout"><p>$ git log --no-merges t/</p></div><p>In the pager (<code class="literal">less</code>), just search for "bundle", go a few lines back,
1852and see that it is in commit 18449ab0… Now just copy this object name,
1853and paste it into the command line</p><div class="literallayout"><p>$ git show 18449ab0</p></div><p>Voila.</p><p>Another example: Find out what to do in order to make some script a
1854builtin:</p><div class="literallayout"><p>$ git log --no-merges --diff-filter=A builtin-*.c</p></div><p>You see, Git is actually the best tool to find out about the source of Git
Junio C Hamano9810d632007-09-24 01:05:34[diff] [blame]1855itself!</p></div></div><div class="chapter" lang="en"><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]1856<a name="def_alternate_object_database"></a>alternate object database
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1857</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1858 Via the alternates mechanism, a <a class="link" href="#def_repository">repository</a>
1859 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]1860 from another object database, which is called "alternate".
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1861</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1862<a name="def_bare_repository"></a>bare repository
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1863</span></dt><dd>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1864 A bare repository is normally an appropriately
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1865 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]1866 have a locally checked-out copy of any of the files under
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]1867 revision control. That is, all of the <code class="literal">git</code>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1868 administrative and control files that would normally be present in the
1869 hidden <code class="literal">.git</code> sub-directory are directly present in the
1870 <code class="literal">repository.git</code> directory instead,
1871 and no other files are present and checked out. Usually publishers of
1872 public repositories make bare repositories available.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1873</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1874<a name="def_blob_object"></a>blob object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1875</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1876 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]1877</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1878<a name="def_branch"></a>branch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1879</span></dt><dd>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1880 A "branch" is an active line of development. The most recent
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1881 <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]1882 that branch. The tip of the branch is referenced by a branch
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1883 <a class="link" href="#def_head">head</a>, which moves forward as additional development
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1884 is done on the branch. A single git
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1885 <a class="link" href="#def_repository">repository</a> can track an arbitrary number of
1886 branches, but your <a class="link" href="#def_working_tree">working tree</a> is
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1887 associated with just one of them (the "current" or "checked out"
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1888 branch), and <a class="link" href="#def_HEAD">HEAD</a> points to that branch.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1889</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1890<a name="def_cache"></a>cache
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1891</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1892 Obsolete for: <a class="link" href="#def_index">index</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1893</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1894<a name="def_chain"></a>chain
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1895</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1896 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]1897 a reference to its successor (for example, the successor of a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1898 <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]1899</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1900<a name="def_changeset"></a>changeset
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1901</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1902 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]1903 store changes, but states, it really does not make sense to use the term
1904 "changesets" with git.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1905</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1906<a name="def_checkout"></a>checkout
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1907</span></dt><dd>
Junio C Hamanoa14a4032008-03-25 09:11:02[diff] [blame]1908 The action of updating all or part of the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1909 <a class="link" href="#def_working_tree">working tree</a> with a <a class="link" href="#def_tree_object">tree object</a>
1910 or <a class="link" href="#def_blob_object">blob</a> from the
1911 <a class="link" href="#def_object_database">object database</a>, and updating the
1912 <a class="link" href="#def_index">index</a> and <a class="link" href="#def_HEAD">HEAD</a> if the whole working tree has
1913 been pointed at a new <a class="link" href="#def_branch">branch</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1914</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1915<a name="def_cherry-picking"></a>cherry-picking
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1916</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1917 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]1918 changes out of a series of changes (typically commits) and record them
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]1919 as a new series of changes on top of a different codebase. In GIT, this is
1920 performed by the "git cherry-pick" command to extract the change introduced
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1921 by an existing <a class="link" href="#def_commit">commit</a> and to record it based on the tip
1922 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]1923</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1924<a name="def_clean"></a>clean
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1925</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1926 A <a class="link" href="#def_working_tree">working tree</a> is clean, if it
1927 corresponds to the <a class="link" href="#def_revision">revision</a> referenced by the current
1928 <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]1929</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1930<a name="def_commit"></a>commit
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1931</span></dt><dd><p>
1932 As a noun: A single point in the
1933 git history; the entire history of a project is represented as a
1934 set of interrelated commits. The word "commit" is often
1935 used by git in the same places other revision control systems
1936 use the words "revision" or "version". Also used as a short
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1937 hand for <a class="link" href="#def_commit_object">commit object</a>.
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1938</p><p>As a verb: The action of storing a new snapshot of the project's
1939state in the git history, by creating a new commit representing the current
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1940state 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]1941to point at the new commit.</p></dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1942<a name="def_commit_object"></a>commit object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1943</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1944 An <a class="link" href="#def_object">object</a> which contains the information about a
1945 particular <a class="link" href="#def_revision">revision</a>, such as <a class="link" href="#def_parent">parents</a>, committer,
1946 author, date and the <a class="link" href="#def_tree_object">tree object</a> which corresponds
1947 to the top <a class="link" href="#def_directory">directory</a> of the stored
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]1948 revision.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1949</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1950<a name="def_core_git"></a>core git
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1951</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1952 Fundamental data structures and utilities of git. Exposes only limited
1953 source code management tools.
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_DAG"></a>DAG
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 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]1958 directed acyclic graph, because they have parents (directed), and the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1959 graph of commit objects is acyclic (there is no <a class="link" href="#def_chain">chain</a>
1960 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]1961</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1962<a name="def_dangling_object"></a>dangling object
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]1963</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1964 An <a class="link" href="#def_unreachable_object">unreachable object</a> which is not
1965 <a class="link" href="#def_reachable">reachable</a> even from other unreachable objects; a
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1966 dangling object has no references to it from any
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1967 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]1968</dd><dt><span class="term">
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1969<a name="def_detached_HEAD"></a>detached HEAD
1970</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1971 Normally the <a class="link" href="#def_HEAD">HEAD</a> stores the name of a
1972 <a class="link" href="#def_branch">branch</a>. However, git also allows you to <a class="link" href="#def_checkout">check out</a>
1973 an arbitrary <a class="link" href="#def_commit">commit</a> that isn't necessarily the tip of any
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]1974 particular branch. In this case HEAD is said to be "detached".
1975</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1976<a name="def_dircache"></a>dircache
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1977</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1978 You are <span class="strong"><strong>waaaaay</strong></span> behind. See <a class="link" href="#def_index">index</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1979</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1980<a name="def_directory"></a>directory
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1981</span></dt><dd>
1982 The list you get with "ls" :-)
1983</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1984<a name="def_dirty"></a>dirty
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1985</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1986 A <a class="link" href="#def_working_tree">working tree</a> is said to be "dirty" if
1987 it contains modifications which have not been <a class="link" href="#def_commit">committed</a> to the current
1988 <a class="link" href="#def_branch">branch</a>.
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1989</dd><dt><span class="term">
1990<a name="def_ent"></a>ent
1991</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1992 Favorite synonym to "<a class="link" href="#def_tree-ish">tree-ish</a>" by some total geeks. See
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1993 <code class="literal">http://en.wikipedia.org/wiki/Ent_(Middle-earth)</code> for an in-depth
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]1994 explanation. Avoid this term, not to confuse people.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]1995</dd><dt><span class="term">
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]1996<a name="def_evil_merge"></a>evil merge
1997</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]1998 An evil merge is a <a class="link" href="#def_merge">merge</a> that introduces changes that
1999 do not appear in any <a class="link" href="#def_parent">parent</a>.
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2000</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2001<a name="def_fast_forward"></a>fast forward
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2002</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2003 A fast-forward is a special type of <a class="link" href="#def_merge">merge</a> where you have a
2004 <a class="link" href="#def_revision">revision</a> and you are "merging" another
2005 <a class="link" href="#def_branch">branch</a>'s changes that happen to be a descendant of what
2006 you have. In such these cases, you do not make a new <a class="link" href="#def_merge">merge</a>
2007 <a class="link" href="#def_commit">commit</a> but instead just update to his
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2008 revision. This will happen frequently on a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2009 <a class="link" href="#def_tracking_branch">tracking branch</a> of a remote
2010 <a class="link" href="#def_repository">repository</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2011</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2012<a name="def_fetch"></a>fetch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2013</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2014 Fetching a <a class="link" href="#def_branch">branch</a> means to get the
2015 branch's <a class="link" href="#def_head_ref">head ref</a> from a remote
2016 <a class="link" href="#def_repository">repository</a>, to find out which objects are
2017 missing from the local <a class="link" href="#def_object_database">object database</a>,
2018 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]2019</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2020<a name="def_file_system"></a>file system
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2021</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2022 Linus Torvalds originally designed git to be a user space file system,
2023 i.e. the infrastructure to hold files and directories. That ensured the
2024 efficiency and speed of git.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2025</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2026<a name="def_git_archive"></a>git archive
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2027</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2028 Synonym for <a class="link" href="#def_repository">repository</a> (for arch people).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2029</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2030<a name="def_grafts"></a>grafts
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2031</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2032 Grafts enables two otherwise different lines of development to be joined
2033 together by recording fake ancestry information for commits. This way
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2034 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]2035 is different from what was recorded when the commit was
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2036 created. Configured via the <code class="literal">.git/info/grafts</code> file.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2037</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2038<a name="def_hash"></a>hash
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2039</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2040 In git's context, synonym to <a class="link" href="#def_object_name">object name</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2041</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2042<a name="def_head"></a>head
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2043</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2044 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
2045 <a class="link" href="#def_branch">branch</a>. Heads are stored in
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2046 <code class="literal">$GIT_DIR/refs/heads/</code>, except when using packed refs. (See
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2047 <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]2048</dd><dt><span class="term">
2049<a name="def_HEAD"></a>HEAD
2050</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2051 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]2052 referred to by HEAD. HEAD is a reference to one of the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2053 <a class="link" href="#def_head">heads</a> in your repository, except when using a
2054 <a class="link" href="#def_detached_HEAD">detached HEAD</a>, in which case it may
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2055 reference an arbitrary commit.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2056</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2057<a name="def_head_ref"></a>head ref
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2058</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2059 A synonym for <a class="link" href="#def_head">head</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2060</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2061<a name="def_hook"></a>hook
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2062</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2063 During the normal execution of several git commands, call-outs are made
2064 to optional scripts that allow a developer to add functionality or
2065 checking. Typically, the hooks allow for a command to be pre-verified
2066 and potentially aborted, and allow for a post-notification after the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2067 operation is done. The hook scripts are found in the
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2068 <code class="literal">$GIT_DIR/hooks/</code> directory, and are enabled by simply
Junio C Hamano116db352008-12-17 19:48:40[diff] [blame]2069 removing the <code class="literal">.sample</code> suffix from the filename. In earlier versions
2070 of git you had to make them executable.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2071</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2072<a name="def_index"></a>index
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2073</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2074 A collection of files with stat information, whose contents are stored
Junio C Hamano36460982007-05-27 04:29:12[diff] [blame]2075 as objects. The index is a stored version of your
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2076 <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]2077 a third version of a working tree, which are used
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2078 when <a class="link" href="#def_merge">merging</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2079</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2080<a name="def_index_entry"></a>index entry
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2081</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2082 The information regarding a particular file, stored in the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2083 <a class="link" href="#def_index">index</a>. An index entry can be unmerged, if a
2084 <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]2085 the index contains multiple versions of that file).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2086</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2087<a name="def_master"></a>master
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2088</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2089 The default development <a class="link" href="#def_branch">branch</a>. Whenever you
2090 create a git <a class="link" href="#def_repository">repository</a>, a branch named
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2091 "master" is created, and becomes the active branch. In most
2092 cases, this contains the local development, though that is
2093 purely by convention and is not required.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2094</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2095<a name="def_merge"></a>merge
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2096</span></dt><dd><p>
2097 As a verb: To bring the contents of another
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2098 <a class="link" href="#def_branch">branch</a> (possibly from an external
2099 <a class="link" href="#def_repository">repository</a>) into the current branch. In the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2100 case where the merged-in branch is from a different repository,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2101 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]2102 and then merging the result into the current branch. This
2103 combination of fetch and merge operations is called a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2104 <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]2105 that identifies changes made since the branches diverged, and
2106 then applies all those changes together. In cases where changes
2107 conflict, manual intervention may be required to complete the
2108 merge.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2109</p><p>As a noun: unless it is a <a class="link" href="#def_fast_forward">fast forward</a>, a
2110successful 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]2111representing the result of the merge, and having as
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2112<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]2113This commit is referred to as a "merge commit", or sometimes just a
2114"merge".</p></dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2115<a name="def_object"></a>object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2116</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2117 The unit of storage in git. It is uniquely identified by the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2118 <a class="link" href="#def_SHA1">SHA1</a> of its contents. Consequently, an
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2119 object can not be changed.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2120</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2121<a name="def_object_database"></a>object database
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 Stores a set of "objects", and an individual <a class="link" href="#def_object">object</a> is
2124 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]2125 live in <code class="literal">$GIT_DIR/objects/</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2126</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2127<a name="def_object_identifier"></a>object identifier
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2128</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2129 Synonym for <a class="link" href="#def_object_name">object name</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2130</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2131<a name="def_object_name"></a>object name
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2132</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2133 The unique identifier of an <a class="link" href="#def_object">object</a>. The <a class="link" href="#def_hash">hash</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2134 of the object's contents using the Secure Hash Algorithm
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2135 1 and usually represented by the 40 character hexadecimal encoding of
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2136 the <a class="link" href="#def_hash">hash</a> of the object.
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_object_type"></a>object type
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2139</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2140 One of the identifiers "<a class="link" href="#def_commit_object">commit</a>",
2141 "<a class="link" href="#def_tree_object">tree</a>", "<a class="link" href="#def_tag_object">tag</a>" or
2142 "<a class="link" href="#def_blob_object">blob</a>" describing the type of an
2143 <a class="link" href="#def_object">object</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2144</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2145<a name="def_octopus"></a>octopus
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2146</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2147 To <a class="link" href="#def_merge">merge</a> more than two <a class="link" href="#def_branch">branches</a>. Also denotes an
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2148 intelligent predator.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2149</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2150<a name="def_origin"></a>origin
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2151</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2152 The default upstream <a class="link" href="#def_repository">repository</a>. Most projects have
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2153 at least one upstream project which they track. By default
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2154 <span class="emphasis"><em>origin</em></span> is used for that purpose. New upstream updates
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2155 will be fetched into remote <a class="link" href="#def_tracking_branch">tracking branches</a> named
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2156 origin/name-of-upstream-branch, which you can see using
Junio C Hamanoea82cff2009-03-18 01:54:48[diff] [blame]2157 <code class="literal">git branch -r</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2158</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2159<a name="def_pack"></a>pack
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2160</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2161 A set of objects which have been compressed into one file (to save space
2162 or to transmit them efficiently).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2163</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2164<a name="def_pack_index"></a>pack index
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2165</span></dt><dd>
2166 The list of identifiers, and other information, of the objects in a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2167 <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]2168 pack.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2169</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2170<a name="def_parent"></a>parent
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2171</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2172 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]2173 of the logical predecessor(s) in the line of development, i.e. its
2174 parents.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2175</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2176<a name="def_pickaxe"></a>pickaxe
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2177</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2178 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]2179 routines that help select changes that add or delete a given text
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]2180 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]2181 <a class="link" href="#def_changeset">changeset</a> that introduced or removed, say, a
2182 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]2183</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2184<a name="def_plumbing"></a>plumbing
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2185</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2186 Cute name for <a class="link" href="#def_core_git">core git</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2187</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2188<a name="def_porcelain"></a>porcelain
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2189</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2190 Cute name for programs and program suites depending on
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2191 <a class="link" href="#def_core_git">core git</a>, presenting a high level access to
2192 core git. Porcelains expose more of a <a class="link" href="#def_SCM">SCM</a>
2193 interface than the <a class="link" href="#def_plumbing">plumbing</a>.
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_pull"></a>pull
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2196</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2197 Pulling a <a class="link" href="#def_branch">branch</a> means to <a class="link" href="#def_fetch">fetch</a> it and
2198 <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]2199</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2200<a name="def_push"></a>push
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2201</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2202 Pushing a <a class="link" href="#def_branch">branch</a> means to get the branch's
2203 <a class="link" href="#def_head_ref">head ref</a> from a remote <a class="link" href="#def_repository">repository</a>,
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]2204 find out if it is a direct ancestor to the branch's local
2205 head ref, and in that case, putting all
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2206 objects, which are <a class="link" href="#def_reachable">reachable</a> from the local
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2207 head ref, and which are missing from the remote
2208 repository, into the remote
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2209 <a class="link" href="#def_object_database">object database</a>, and updating the remote
2210 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]2211 ancestor to the local head, the push fails.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2212</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2213<a name="def_reachable"></a>reachable
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2214</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2215 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]2216 "reachable" from that commit. More
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2217 generally, one <a class="link" href="#def_object">object</a> is reachable from
2218 another if we can reach the one from the other by a <a class="link" href="#def_chain">chain</a>
2219 that follows <a class="link" href="#def_tag">tags</a> to whatever they tag,
2220 <a class="link" href="#def_commit_object">commits</a> to their parents or trees, and
2221 <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]2222 that they contain.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2223</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2224<a name="def_rebase"></a>rebase
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2225</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2226 To reapply a series of changes from a <a class="link" href="#def_branch">branch</a> to a
2227 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]2228 to the result.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2229</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2230<a name="def_ref"></a>ref
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2231</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2232 A 40-byte hex representation of a <a class="link" href="#def_SHA1">SHA1</a> or a name that
2233 denotes a particular <a class="link" href="#def_object">object</a>. These may be stored in
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2234 <code class="literal">$GIT_DIR/refs/</code>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2235</dd><dt><span class="term">
Junio C Hamanobb0f4042007-07-04 06:41:40[diff] [blame]2236<a name="def_reflog"></a>reflog
2237</span></dt><dd>
2238 A reflog shows the local "history" of a ref. In other words,
Junio C Hamano7d3275e2009-05-31 21:53:30[diff] [blame^]2239 it can tell you what the 3rd last revision in _this_ repository
2240 was, and what was the current state in _this_ repository,
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2241 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]2242</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2243<a name="def_refspec"></a>refspec
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2244</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2245 A "refspec" is used by <a class="link" href="#def_fetch">fetch</a> and
2246 <a class="link" href="#def_push">push</a> to describe the mapping between remote
2247 <a class="link" href="#def_ref">ref</a> and local ref. They are combined with a colon in
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2248 the format &lt;src&gt;:&lt;dst&gt;, preceded by an optional plus sign, +.
2249 For example: <code class="literal">git fetch $URL
2250 refs/heads/master:refs/heads/origin</code> means "grab the master
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2251 <a class="link" href="#def_branch">branch</a> <a class="link" href="#def_head">head</a> from the $URL and store
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2252 it as my origin branch head". And <code class="literal">git push
2253 $URL refs/heads/master:refs/heads/to-upstream</code> means "publish my
2254 master branch head as to-upstream branch at $URL". See also
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2255 <a class="ulink" href="git-push.html" target="_top">git-push(1)</a>.
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_repository"></a>repository
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2258</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2259 A collection of <a class="link" href="#def_ref">refs</a> together with an
2260 <a class="link" href="#def_object_database">object database</a> containing all objects
2261 which are <a class="link" href="#def_reachable">reachable</a> from the refs, possibly
2262 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]2263 repository can share an object database with other repositories
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2264 via <a class="link" href="#def_alternate_object_database">alternates mechanism</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2265</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2266<a name="def_resolve"></a>resolve
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2267</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2268 The action of fixing up manually what a failed automatic
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2269 <a class="link" href="#def_merge">merge</a> left behind.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2270</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2271<a name="def_revision"></a>revision
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2272</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2273 A particular state of files and directories which was stored in the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2274 <a class="link" href="#def_object_database">object database</a>. It is referenced by a
2275 <a class="link" href="#def_commit_object">commit object</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2276</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2277<a name="def_rewind"></a>rewind
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2278</span></dt><dd>
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2279 To throw away part of the development, i.e. to assign the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2280 <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]2281</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2282<a name="def_SCM"></a>SCM
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2283</span></dt><dd>
2284 Source code management (tool).
2285</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2286<a name="def_SHA1"></a>SHA1
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2287</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2288 Synonym for <a class="link" href="#def_object_name">object name</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2289</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2290<a name="def_shallow_repository"></a>shallow repository
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2291</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2292 A shallow <a class="link" href="#def_repository">repository</a> has an incomplete
2293 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 Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2294 words, git is told to pretend that these commits do not have the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2295 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]2296 recent history of a project even though the real history recorded in the
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2297 upstream is much larger. A shallow repository
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2298 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
2299 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]2300</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2301<a name="def_symref"></a>symref
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2302</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2303 Symbolic reference: instead of containing the <a class="link" href="#def_SHA1">SHA1</a>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2304 id itself, it is of the format <span class="emphasis"><em>ref: refs/some/thing</em></span> and when
2305 referenced, it recursively dereferences to this reference.
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2306 <span class="emphasis"><em><a class="link" href="#def_HEAD">HEAD</a></em></span> is a prime example of a symref. Symbolic
2307 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]2308 command.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2309</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2310<a name="def_tag"></a>tag
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2311</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2312 A <a class="link" href="#def_ref">ref</a> pointing to a <a class="link" href="#def_tag_object">tag</a> or
2313 <a class="link" href="#def_commit_object">commit object</a>. In contrast to a <a class="link" href="#def_head">head</a>,
2314 a tag is not changed by a <a class="link" href="#def_commit">commit</a>. Tags (not
2315 <a class="link" href="#def_tag_object">tag objects</a>) are stored in <code class="literal">$GIT_DIR/refs/tags/</code>. A
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2316 git tag has nothing to do with a Lisp tag (which would be
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2317 called an <a class="link" href="#def_object_type">object type</a> in git's context). A
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2318 tag is most typically used to mark a particular point in the
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2319 commit ancestry <a class="link" href="#def_chain">chain</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2320</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2321<a name="def_tag_object"></a>tag object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2322</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2323 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]2324 another object, which can contain a message just like a
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2325 <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]2326 signature, in which case it is called a "signed tag object".
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2327</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2328<a name="def_topic_branch"></a>topic branch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2329</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2330 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]2331 identify a conceptual line of development. Since branches are very easy
2332 and inexpensive, it is often desirable to have several small branches
2333 that each contain very well defined concepts or small incremental yet
2334 related changes.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2335</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2336<a name="def_tracking_branch"></a>tracking branch
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2337</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2338 A regular git <a class="link" href="#def_branch">branch</a> that is used to follow changes from
2339 another <a class="link" href="#def_repository">repository</a>. A tracking
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2340 branch should not contain direct modifications or have local commits
2341 made to it. A tracking branch can usually be
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2342 identified as the right-hand-side <a class="link" href="#def_ref">ref</a> in a Pull:
2343 <a class="link" href="#def_refspec">refspec</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2344</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2345<a name="def_tree"></a>tree
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 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]2348 (i.e. a stored representation of a working tree).
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2349</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2350<a name="def_tree_object"></a>tree object
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2351</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2352 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]2353 with refs to the associated blob and/or tree objects. A
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2354 <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]2355</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2356<a name="def_tree-ish"></a>tree-ish
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2357</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2358 A <a class="link" href="#def_ref">ref</a> pointing to either a <a class="link" href="#def_commit_object">commit object</a>, a <a class="link" href="#def_tree_object">tree object</a>, or a <a class="link" href="#def_tag_object">tag object</a> pointing to a tag or commit or tree object.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2359</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2360<a name="def_unmerged_index"></a>unmerged index
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2361</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2362 An <a class="link" href="#def_index">index</a> which contains unmerged
2363 <a class="link" href="#def_index_entry">index entries</a>.
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2364</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2365<a name="def_unreachable_object"></a>unreachable object
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2366</span></dt><dd>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2367 An <a class="link" href="#def_object">object</a> which is not <a class="link" href="#def_reachable">reachable</a> from a
2368 <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]2369</dd><dt><span class="term">
Junio C Hamano98e32c32009-04-13 02:39:53[diff] [blame]2370<a name="def_upstream_branch"></a>upstream branch
2371</span></dt><dd>
2372 The default <a class="link" href="#def_branch">branch</a> that is merged into the branch in
2373 question (or the branch in question is rebased onto). It is configured
2374 via branch.&lt;name&gt;.remote and branch.&lt;name&gt;.merge. If the upstream branch
2375 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>".
2376</dd><dt><span class="term">
Junio C Hamano3d5b41f2007-03-26 02:33:41[diff] [blame]2377<a name="def_working_tree"></a>working tree
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2378</span></dt><dd>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2379 The tree of actual checked out files. The working tree is
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2380 normally equal to the <a class="link" href="#def_HEAD">HEAD</a> plus any local changes
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2381 that you have made but not yet committed.
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]2382</dd></dl></div></div><div class="appendix" lang="en"><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
2383explain how these work in more detail.</p><div class="section" lang="en"><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><div class="literallayout"><p>$ tar xzf project.tar.gz<br>
2384$ cd project<br>
2385$ git init<br>
2386Initialized empty Git repository in .git/<br>
2387$ git add .<br>
2388$ git commit</p></div><p>From a remote repository:</p><div class="literallayout"><p>$ git clone git://example.com/pub/project.git<br>
2389$ cd project</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="managing-branches"></a>Managing branches</h2></div></div></div><div class="literallayout"><p>$ git branch         # list all local branches in this repo<br>
2390$ git checkout test  # switch working directory to branch "test"<br>
2391$ git branch new     # create branch "new" starting at current HEAD<br>
Junio C Hamano764a6672007-10-23 01:23:31[diff] [blame]2392$ git branch -d new  # delete branch "new"</p></div><p>Instead of basing a new branch on current HEAD (the default), use:</p><div class="literallayout"><p>$ git branch new test    # branch named "test"<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]2393$ git branch new v2.6.15 # tag named v2.6.15<br>
2394$ git branch new HEAD^   # commit before the most recent<br>
2395$ git branch new HEAD^^  # commit before that<br>
2396$ git branch new test~10 # ten commits before tip of branch "test"</p></div><p>Create and switch to a new branch at the same time:</p><div class="literallayout"><p>$ git checkout -b new v2.6.15</p></div><p>Update and examine branches from the repository you cloned from:</p><div class="literallayout"><p>$ git fetch             # update<br>
2397$ git branch -r         # list<br>
2398  origin/master<br>
2399  origin/next<br>
2400  ...<br>
2401$ git checkout -b masterwork origin/master</p></div><p>Fetch a branch from a different repository, and give it a new
2402name in your repository:</p><div class="literallayout"><p>$ git fetch git://example.com/project.git theirbranch:mybranch<br>
2403$ git fetch git://example.com/project.git v2.6.15:mybranch</p></div><p>Keep a list of repositories you work with regularly:</p><div class="literallayout"><p>$ git remote add example git://example.com/project.git<br>
2404$ git remote                    # list remote repositories<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2405example<br>
2406origin<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]2407$ git remote show example       # get details<br>
2408* remote example<br>
2409  URL: git://example.com/project.git<br>
2410  Tracked remote branches<br>
Junio C Hamanoedc174c2008-10-23 05:18:54[diff] [blame]2411    master<br>
2412    next<br>
2413    ...<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]2414$ git fetch example             # update branches from example<br>
2415$ git branch -r                 # list all remote branches</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exploring-history"></a>Exploring history</h2></div></div></div><div class="literallayout"><p>$ gitk                      # visualize and browse history<br>
2416$ git log                   # list all commits<br>
2417$ git log src/              # ...modifying src/<br>
2418$ git log v2.6.15..v2.6.16  # ...in v2.6.16, not in v2.6.15<br>
2419$ git log master..test      # ...in branch test, not in branch master<br>
2420$ git log test..master      # ...in branch master, but not in test<br>
2421$ git log test...master     # ...in one branch, not in both<br>
2422$ git log -S'foo()'         # ...where difference contain "foo()"<br>
2423$ git log --since="2 weeks ago"<br>
2424$ git log -p                # show patches as well<br>
2425$ git show                  # most recent commit<br>
2426$ git diff v2.6.15..v2.6.16 # diff between two tagged versions<br>
2427$ git diff v2.6.15..HEAD    # diff with current head<br>
2428$ git grep "foo()"          # search working directory for "foo()"<br>
2429$ git grep v2.6.15 "foo()"  # search old tree for "foo()"<br>
2430$ git show v2.6.15:a.txt    # look at old version of a.txt</p></div><p>Search for regressions:</p><div class="literallayout"><p>$ git bisect start<br>
2431$ git bisect bad                # current version is bad<br>
2432$ git bisect good v2.6.13-rc2   # last known good revision<br>
2433Bisecting: 675 revisions left to test after this<br>
2434                                # test here, then:<br>
2435$ git bisect good               # if this revision is good, or<br>
2436$ git bisect bad                # if this revision is bad.<br>
2437                                # repeat until done.</p></div></div><div class="section" lang="en"><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><div class="literallayout"><p>$ cat &gt;&gt;~/.gitconfig &lt;&lt;\EOF<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2438[user]<br>
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]2439        name = Your Name Comes Here<br>
2440        email = you@yourdomain.example.com<br>
Junio C Hamano75485c82007-05-19 04:20:33[diff] [blame]2441EOF</p></div><p>Select file contents to include in the next commit, then make the
Junio C Hamanocc13f552007-07-24 08:59:43[diff] [blame]2442commit:</p><div class="literallayout"><p>$ git add a.txt    # updated file<br>
2443$ git add b.txt    # new file<br>
2444$ git rm c.txt     # old file<br>
2445$ git commit</p></div><p>Or, prepare and create the commit in one step:</p><div class="literallayout"><p>$ git commit d.txt # use latest content only of d.txt<br>
2446$ git commit -a    # use latest content of all tracked files</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="merging"></a>Merging</h2></div></div></div><div class="literallayout"><p>$ git merge test   # merge branch "test" into the current branch<br>
2447$ git pull git://example.com/project.git master<br>
2448                   # fetch and merge in remote branch<br>
2449$ git pull . test  # equivalent to git merge test</p></div></div><div class="section" lang="en"><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><div class="literallayout"><p>$ git format-patch origin..HEAD # format a patch for each commit<br>
2450                                # in HEAD but not in origin<br>
2451$ git am mbox # import patches from the mailbox "mbox"</p></div><p>Fetch a branch in a different git repository, then merge into the
2452current branch:</p><div class="literallayout"><p>$ git pull git://example.com/project.git theirbranch</p></div><p>Store the fetched branch into a local branch before merging into the
2453current branch:</p><div class="literallayout"><p>$ git pull git://example.com/project.git theirbranch:mybranch</p></div><p>After creating commits on a local branch, update the remote
2454branch with your commits:</p><div class="literallayout"><p>$ git push ssh://example.com/project.git mybranch:theirbranch</p></div><p>When remote and local branch are both named "test":</p><div class="literallayout"><p>$ git push ssh://example.com/project.git test</p></div><p>Shortcut version for a frequently used remote repository:</p><div class="literallayout"><p>$ git remote add example ssh://example.com/project.git<br>
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2455$ git push example test</p></div></div><div class="section" lang="en"><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><div class="literallayout"><p>$ git fsck</p></div><p>Recompress, remove unused cruft:</p><div class="literallayout"><p>$ git gc</p></div></div></div><div class="appendix" lang="en"><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 type="disc"><li>
2456It must be readable in order, from beginning to end, by someone
2457 intelligent with a basic grasp of the UNIX command line, but without
2458 any special knowledge of git. If necessary, any other prerequisites
2459 should be specifically mentioned as they arise.
2460</li><li>
2461Whenever possible, section headings should clearly describe the task
2462 they explain how to do, in language that requires no more knowledge
2463 than necessary: for example, "importing patches into a project" rather
Junio C Hamano5f9a6f02009-04-06 08:26:56[diff] [blame]2464 than "the <code class="literal">git am</code> command"
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2465</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]2466allow people to get to important topics without necessarily reading
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2467everything in between.</p><p>Scan Documentation/ for other stuff left out; in particular:</p><div class="itemizedlist"><ul type="disc"><li>
2468howto's
2469</li><li>
2470some of technical/?
2471</li><li>
2472hooks
2473</li><li>
Junio C Hamanoba4b9282008-07-06 05:20:31[diff] [blame]2474list of commands in <a class="ulink" href="git.html" target="_top">git(1)</a>
Junio C Hamano597ffcf2007-09-17 17:33:15[diff] [blame]2475</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]2476provides.</p><p>Simplify beginning by suggesting disconnected head instead of
Junio C Hamanoaa83a7d2007-03-05 02:37:29[diff] [blame]2477temporary branch creation?</p><p>Add more good examples. Entire sections of just cookbook examples
Junio C Hamano8f62db92007-02-01 00:22:22[diff] [blame]2478might be a good idea; maybe make an "advanced examples" section a
2479standard 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]2480documentation.</p><p>Add a section on working with other version control systems, including
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]2481CVS, 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:
2482 http://marc.theaimsgroup.com/?l=git&amp;m=117263864820799&amp;w=2
Junio C Hamanoce3650e2007-11-26 04:20:11[diff] [blame]2483 http://marc.theaimsgroup.com/?l=git&amp;m=117147855503798&amp;w=2</p></div></div></body></html>