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Junio C Hamanoe6f28d02013-09-17 21:34:001Git User Manual
Junio C Hamano21bc18b2014-01-10 20:33:072===============
Junio C Hamano75485c82007-05-19 04:20:333
4Git is a fast distributed revision control system.
5
Junio C Hamanoa6387422007-08-25 03:54:276This manual is designed to be readable by someone with basic UNIX
Junio C Hamano076ffcc2013-02-06 05:13:217command-line skills, but no previous knowledge of Git.
Junio C Hamano8f62db92007-02-01 00:22:228
Junio C Hamano75485c82007-05-19 04:20:339<<repositories-and-branches>> and <<exploring-git-history>> explain how
10to fetch and study a project using git--read these chapters to learn how
11to build and test a particular version of a software project, search for
12regressions, and so on.
Junio C Hamano8f62db92007-02-01 00:22:2213
Junio C Hamano75485c82007-05-19 04:20:3314People needing to do actual development will also want to read
Junio C Hamanoec87f522008-12-10 08:35:2515<<Developing-With-git>> and <<sharing-development>>.
Junio C Hamano8f62db92007-02-01 00:22:2216
17Further chapters cover more specialized topics.
18
19Comprehensive reference documentation is available through the man
Junio C Hamanof66ecee2008-11-17 18:25:4320pages, or linkgit:git-help[1] command. For example, for the command
Junio C Hamano947ab822013-03-19 23:07:2921`git clone <repo>`, you can either use:
Junio C Hamano8f62db92007-02-01 00:22:2222
23------------------------------------------------
24$ man git-clone
25------------------------------------------------
26
Junio C Hamanof66ecee2008-11-17 18:25:4327or:
28
29------------------------------------------------
30$ git help clone
31------------------------------------------------
32
33With the latter, you can use the manual viewer of your choice; see
34linkgit:git-help[1] for more information.
35
Junio C Hamano076ffcc2013-02-06 05:13:2136See also <<git-quick-start>> for a brief overview of Git commands,
Junio C Hamano75485c82007-05-19 04:20:3337without any explanation.
Junio C Hamano8f62db92007-02-01 00:22:2238
Junio C Hamanof614c642007-06-11 01:21:5439Finally, see <<todo>> for ways that you can help make this manual more
Junio C Hamano75485c82007-05-19 04:20:3340complete.
Junio C Hamano8f62db92007-02-01 00:22:2241
Junio C Hamano8f62db92007-02-01 00:22:2242
Junio C Hamano3d30fd52007-05-08 00:32:5343[[repositories-and-branches]]
Junio C Hamano8f62db92007-02-01 00:22:2244Repositories and Branches
45=========================
46
Junio C Hamano3d30fd52007-05-08 00:32:5347[[how-to-get-a-git-repository]]
Junio C Hamano076ffcc2013-02-06 05:13:2148How to get a Git repository
Junio C Hamano8f62db92007-02-01 00:22:2249---------------------------
50
Junio C Hamano076ffcc2013-02-06 05:13:2151It will be useful to have a Git repository to experiment with as you
Junio C Hamano8f62db92007-02-01 00:22:2252read this manual.
53
Junio C Hamano35738e82008-01-07 07:55:4654The best way to get one is by using the linkgit:git-clone[1] command to
Junio C Hamano8b8b0f22007-08-26 22:10:2655download a copy of an existing repository. If you don't already have a
56project in mind, here are some interesting examples:
Junio C Hamano8f62db92007-02-01 00:22:2257
58------------------------------------------------
Junio C Hamano3a3357e2013-06-26 23:20:5659# Git itself (approx. 40MB download):
Junio C Hamano8f62db92007-02-01 00:22:2260$ git clone git://git.kernel.org/pub/scm/git/git.git
Junio C Hamano3a3357e2013-06-26 23:20:5661# the Linux kernel (approx. 640MB download):
62$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Junio C Hamano8f62db92007-02-01 00:22:2263------------------------------------------------
64
65The initial clone may be time-consuming for a large project, but you
66will only need to clone once.
67
Junio C Hamanoa1952302013-07-01 21:31:1868The clone command creates a new directory named after the project
69(`git` or `linux` in the examples above). After you cd into this
Junio C Hamano8f62db92007-02-01 00:22:2270directory, you will see that it contains a copy of the project files,
Junio C Hamanoce3650e2007-11-26 04:20:1171called the <<def_working_tree,working tree>>, together with a special
Junio C Hamano947ab822013-03-19 23:07:2972top-level directory named `.git`, which contains all the information
Junio C Hamanoce3650e2007-11-26 04:20:1173about the history of the project.
Junio C Hamano8f62db92007-02-01 00:22:2274
Junio C Hamano3d30fd52007-05-08 00:32:5375[[how-to-check-out]]
Junio C Hamano8f62db92007-02-01 00:22:2276How to check out a different version of a project
77-------------------------------------------------
78
Junio C Hamano8b8b0f22007-08-26 22:10:2679Git is best thought of as a tool for storing the history of a collection
80of files. It stores the history as a compressed collection of
Junio C Hamano076ffcc2013-02-06 05:13:2181interrelated snapshots of the project's contents. In Git each such
Junio C Hamano8b8b0f22007-08-26 22:10:2682version is called a <<def_commit,commit>>.
Junio C Hamano8f62db92007-02-01 00:22:2283
Junio C Hamanoce3650e2007-11-26 04:20:1184Those snapshots aren't necessarily all arranged in a single line from
85oldest to newest; instead, work may simultaneously proceed along
Junio C Hamano618bdde2008-01-02 10:51:0886parallel lines of development, called <<def_branch,branches>>, which may
Junio C Hamanoce3650e2007-11-26 04:20:1187merge and diverge.
88
Junio C Hamano076ffcc2013-02-06 05:13:2189A single Git repository can track development on multiple branches. It
Junio C Hamanoce3650e2007-11-26 04:20:1190does this by keeping a list of <<def_head,heads>> which reference the
Junio C Hamano35738e82008-01-07 07:55:4691latest commit on each branch; the linkgit:git-branch[1] command shows
Junio C Hamano3d5b41f2007-03-26 02:33:4192you the list of branch heads:
Junio C Hamano8f62db92007-02-01 00:22:2293
94------------------------------------------------
95$ git branch
96* master
97------------------------------------------------
98
Junio C Hamano0e3cb532007-04-17 08:28:1199A freshly cloned repository contains a single branch head, by default
100named "master", with the working directory initialized to the state of
101the project referred to by that branch head.
Junio C Hamano8f62db92007-02-01 00:22:22102
Junio C Hamano3d5b41f2007-03-26 02:33:41103Most projects also use <<def_tag,tags>>. Tags, like heads, are
104references into the project's history, and can be listed using the
Junio C Hamano35738e82008-01-07 07:55:46105linkgit:git-tag[1] command:
Junio C Hamano8f62db92007-02-01 00:22:22106
107------------------------------------------------
108$ git tag -l
109v2.6.11
110v2.6.11-tree
111v2.6.12
112v2.6.12-rc2
113v2.6.12-rc3
114v2.6.12-rc4
115v2.6.12-rc5
116v2.6.12-rc6
117v2.6.13
118...
119------------------------------------------------
120
121Tags are expected to always point at the same version of a project,
Junio C Hamano3d5b41f2007-03-26 02:33:41122while heads are expected to advance as development progresses.
Junio C Hamano8f62db92007-02-01 00:22:22123
Junio C Hamano3d5b41f2007-03-26 02:33:41124Create a new branch head pointing to one of these versions and check it
Junio C Hamano35738e82008-01-07 07:55:46125out using linkgit:git-checkout[1]:
Junio C Hamano8f62db92007-02-01 00:22:22126
127------------------------------------------------
128$ git checkout -b new v2.6.13
129------------------------------------------------
130
131The working directory then reflects the contents that the project had
Junio C Hamano35738e82008-01-07 07:55:46132when it was tagged v2.6.13, and linkgit:git-branch[1] shows two
Junio C Hamano8f62db92007-02-01 00:22:22133branches, with an asterisk marking the currently checked-out branch:
134
135------------------------------------------------
136$ git branch
137 master
138* new
139------------------------------------------------
140
141If you decide that you'd rather see version 2.6.17, you can modify
142the current branch to point at v2.6.17 instead, with
143
144------------------------------------------------
145$ git reset --hard v2.6.17
146------------------------------------------------
147
Junio C Hamano3d5b41f2007-03-26 02:33:41148Note that if the current branch head was your only reference to a
Junio C Hamano8f62db92007-02-01 00:22:22149particular point in history, then resetting that branch may leave you
Junio C Hamano3d5b41f2007-03-26 02:33:41150with no way to find the history it used to point to; so use this command
151carefully.
Junio C Hamano8f62db92007-02-01 00:22:22152
Junio C Hamano3d30fd52007-05-08 00:32:53153[[understanding-commits]]
Junio C Hamano8f62db92007-02-01 00:22:22154Understanding History: Commits
155------------------------------
156
157Every change in the history of a project is represented by a commit.
Junio C Hamano35738e82008-01-07 07:55:46158The linkgit:git-show[1] command shows the most recent commit on the
Junio C Hamano8f62db92007-02-01 00:22:22159current branch:
160
161------------------------------------------------
162$ git show
Junio C Hamano8b8b0f22007-08-26 22:10:26163commit 17cf781661e6d38f737f15f53ab552f1e95960d7
164Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)>
165Date: Tue Apr 19 14:11:06 2005 -0700
Junio C Hamano8f62db92007-02-01 00:22:22166
Junio C Hamano8b8b0f22007-08-26 22:10:26167 Remove duplicate getenv(DB_ENVIRONMENT) call
Junio C Hamanoa77a5132007-06-08 16:13:44168
Junio C Hamano8b8b0f22007-08-26 22:10:26169 Noted by Tony Luck.
Junio C Hamanoa77a5132007-06-08 16:13:44170
Junio C Hamano8b8b0f22007-08-26 22:10:26171diff --git a/init-db.c b/init-db.c
172index 65898fa..b002dc6 100644
173--- a/init-db.c
174+++ b/init-db.c
175@@ -7,7 +7,7 @@
176
177 int main(int argc, char **argv)
178 {
179- char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
180+ char *sha1_dir, *path;
181 int len, i;
182
183 if (mkdir(".git", 0755) < 0) {
Junio C Hamano8f62db92007-02-01 00:22:22184------------------------------------------------
185
186As you can see, a commit shows who made the latest change, what they
187did, and why.
188
Junio C Hamanoaa83a7d2007-03-05 02:37:29189Every commit has a 40-hexdigit id, sometimes called the "object name" or the
Junio C Hamano947ab822013-03-19 23:07:29190"SHA-1 id", shown on the first line of the `git show` output. You can usually
Junio C Hamanoaa83a7d2007-03-05 02:37:29191refer to a commit by a shorter name, such as a tag or a branch name, but this
192longer name can also be useful. Most importantly, it is a globally unique
193name for this commit: so if you tell somebody else the object name (for
194example in email), then you are guaranteed that name will refer to the same
195commit in their repository that it does in yours (assuming their repository
196has that commit at all). Since the object name is computed as a hash over the
197contents of the commit, you are guaranteed that the commit can never change
198without its name also changing.
199
Junio C Hamano076ffcc2013-02-06 05:13:21200In fact, in <<git-concepts>> we shall see that everything stored in Git
Junio C Hamanoaa83a7d2007-03-05 02:37:29201history, including file data and directory contents, is stored in an object
202with a name that is a hash of its contents.
Junio C Hamano8f62db92007-02-01 00:22:22203
Junio C Hamano3d30fd52007-05-08 00:32:53204[[understanding-reachability]]
Junio C Hamano8f62db92007-02-01 00:22:22205Understanding history: commits, parents, and reachability
206~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
207
208Every commit (except the very first commit in a project) also has a
209parent commit which shows what happened before this commit.
210Following the chain of parents will eventually take you back to the
211beginning of the project.
212
Junio C Hamano076ffcc2013-02-06 05:13:21213However, the commits do not form a simple list; Git allows lines of
Junio C Hamano8f62db92007-02-01 00:22:22214development to diverge and then reconverge, and the point where two
215lines of development reconverge is called a "merge". The commit
216representing a merge can therefore have more than one parent, with
217each parent representing the most recent commit on one of the lines
218of development leading to that point.
219
Junio C Hamano35738e82008-01-07 07:55:46220The best way to see how this works is using the linkgit:gitk[1]
Junio C Hamano076ffcc2013-02-06 05:13:21221command; running gitk now on a Git repository and looking for merge
Junio C Hamanoe6f28d02013-09-17 21:34:00222commits will help understand how Git organizes history.
Junio C Hamano8f62db92007-02-01 00:22:22223
224In the following, we say that commit X is "reachable" from commit Y
225if commit X is an ancestor of commit Y. Equivalently, you could say
Junio C Hamanoa6387422007-08-25 03:54:27226that Y is a descendant of X, or that there is a chain of parents
Junio C Hamano8f62db92007-02-01 00:22:22227leading from commit Y to commit X.
228
Junio C Hamano3d30fd52007-05-08 00:32:53229[[history-diagrams]]
Junio C Hamanoee1e4282007-02-04 08:32:04230Understanding history: History diagrams
231~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:22232
Junio C Hamano076ffcc2013-02-06 05:13:21233We will sometimes represent Git history using diagrams like the one
Junio C Hamano8f62db92007-02-01 00:22:22234below. Commits are shown as "o", and the links between them with
235lines drawn with - / and \. Time goes left to right:
236
Junio C Hamanoc51fede2007-03-12 07:29:20237
238................................................
Junio C Hamano8f62db92007-02-01 00:22:22239 o--o--o <-- Branch A
240 /
241 o--o--o <-- master
242 \
243 o--o--o <-- Branch B
Junio C Hamanoc51fede2007-03-12 07:29:20244................................................
Junio C Hamano8f62db92007-02-01 00:22:22245
246If we need to talk about a particular commit, the character "o" may
247be replaced with another letter or number.
248
Junio C Hamano3d30fd52007-05-08 00:32:53249[[what-is-a-branch]]
Junio C Hamano8f62db92007-02-01 00:22:22250Understanding history: What is a branch?
251~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
252
Junio C Hamano3d5b41f2007-03-26 02:33:41253When we need to be precise, we will use the word "branch" to mean a line
254of development, and "branch head" (or just "head") to mean a reference
255to the most recent commit on a branch. In the example above, the branch
256head named "A" is a pointer to one particular commit, but we refer to
257the line of three commits leading up to that point as all being part of
Junio C Hamano8f62db92007-02-01 00:22:22258"branch A".
259
Junio C Hamano3d5b41f2007-03-26 02:33:41260However, when no confusion will result, we often just use the term
261"branch" both for branches and for branch heads.
Junio C Hamano8f62db92007-02-01 00:22:22262
Junio C Hamano3d30fd52007-05-08 00:32:53263[[manipulating-branches]]
Junio C Hamano8f62db92007-02-01 00:22:22264Manipulating branches
265---------------------
266
267Creating, deleting, and modifying branches is quick and easy; here's
268a summary of the commands:
269
Junio C Hamano947ab822013-03-19 23:07:29270`git branch`::
Junio C Hamanoe6f28d02013-09-17 21:34:00271list all branches.
Junio C Hamano947ab822013-03-19 23:07:29272`git branch <branch>`::
273create a new branch named `<branch>`, referencing the same
Junio C Hamanoe6f28d02013-09-17 21:34:00274point in history as the current branch.
Junio C Hamano947ab822013-03-19 23:07:29275`git branch <branch> <start-point>`::
276create a new branch named `<branch>`, referencing
277`<start-point>`, which may be specified any way you like,
Junio C Hamanoe6f28d02013-09-17 21:34:00278including using a branch name or a tag name.
Junio C Hamano947ab822013-03-19 23:07:29279`git branch -d <branch>`::
Junio C Hamanoe6f28d02013-09-17 21:34:00280delete the branch `<branch>`; if the branch is not fully
281merged in its upstream branch or contained in the current branch,
282this command will fail with a warning.
Junio C Hamano947ab822013-03-19 23:07:29283`git branch -D <branch>`::
Junio C Hamanoe6f28d02013-09-17 21:34:00284delete the branch `<branch>` irrespective of its merged status.
Junio C Hamano947ab822013-03-19 23:07:29285`git checkout <branch>`::
286make the current branch `<branch>`, updating the working
Junio C Hamanoe6f28d02013-09-17 21:34:00287directory to reflect the version referenced by `<branch>`.
Junio C Hamano947ab822013-03-19 23:07:29288`git checkout -b <new> <start-point>`::
289create a new branch `<new>` referencing `<start-point>`, and
Junio C Hamano8f62db92007-02-01 00:22:22290check it out.
291
Junio C Hamano0e3cb532007-04-17 08:28:11292The special symbol "HEAD" can always be used to refer to the current
Junio C Hamano947ab822013-03-19 23:07:29293branch. In fact, Git uses a file named `HEAD` in the `.git` directory
294to remember which branch is current:
Junio C Hamano0e3cb532007-04-17 08:28:11295
296------------------------------------------------
297$ cat .git/HEAD
298ref: refs/heads/master
299------------------------------------------------
300
301[[detached-head]]
302Examining an old version without creating a new branch
303------------------------------------------------------
304
Junio C Hamano5f9a6f02009-04-06 08:26:56305The `git checkout` command normally expects a branch head, but will also
Junio C Hamano0e3cb532007-04-17 08:28:11306accept an arbitrary commit; for example, you can check out the commit
307referenced by a tag:
308
309------------------------------------------------
310$ git checkout v2.6.17
Junio C Hamanoe6f28d02013-09-17 21:34:00311Note: checking out 'v2.6.17'.
312
313You are in 'detached HEAD' state. You can look around, make experimental
314changes and commit them, and you can discard any commits you make in this
315state without impacting any branches by performing another checkout.
316
317If you want to create a new branch to retain commits you create, you may
318do so (now or later) by using -b with the checkout command again. Example:
319
320 git checkout -b new_branch_name
321
Junio C Hamano0e3cb532007-04-17 08:28:11322HEAD is now at 427abfa... Linux v2.6.17
323------------------------------------------------
324
Junio C Hamano5f9a6f02009-04-06 08:26:56325The HEAD then refers to the SHA-1 of the commit instead of to a branch,
Junio C Hamano0e3cb532007-04-17 08:28:11326and git branch shows that you are no longer on a branch:
327
328------------------------------------------------
329$ cat .git/HEAD
330427abfa28afedffadfca9dd8b067eb6d36bac53f
Junio C Hamano3d30fd52007-05-08 00:32:53331$ git branch
Junio C Hamanoe6f28d02013-09-17 21:34:00332* (detached from v2.6.17)
Junio C Hamano0e3cb532007-04-17 08:28:11333 master
334------------------------------------------------
335
336In this case we say that the HEAD is "detached".
337
Junio C Hamano3d30fd52007-05-08 00:32:53338This is an easy way to check out a particular version without having to
339make up a name for the new branch. You can still create a new branch
340(or tag) for this version later if you decide to.
Junio C Hamano8f62db92007-02-01 00:22:22341
Junio C Hamano3d30fd52007-05-08 00:32:53342[[examining-remote-branches]]
Junio C Hamano8f62db92007-02-01 00:22:22343Examining branches from a remote repository
344-------------------------------------------
345
346The "master" branch that was created at the time you cloned is a copy
347of the HEAD in the repository that you cloned from. That repository
348may also have had other branches, though, and your local repository
Junio C Hamano97bcb482010-11-25 03:16:07349keeps branches which track each of those remote branches, called
350remote-tracking branches, which you
Junio C Hamano947ab822013-03-19 23:07:29351can view using the `-r` option to linkgit:git-branch[1]:
Junio C Hamano8f62db92007-02-01 00:22:22352
353------------------------------------------------
354$ git branch -r
355 origin/HEAD
356 origin/html
357 origin/maint
358 origin/man
359 origin/master
360 origin/next
361 origin/pu
362 origin/todo
363------------------------------------------------
364
Junio C Hamano97bcb482010-11-25 03:16:07365In this example, "origin" is called a remote repository, or "remote"
366for short. The branches of this repository are called "remote
367branches" from our point of view. The remote-tracking branches listed
368above were created based on the remote branches at clone time and will
Junio C Hamano947ab822013-03-19 23:07:29369be updated by `git fetch` (hence `git pull`) and `git push`. See
Junio C Hamano97bcb482010-11-25 03:16:07370<<Updating-a-repository-With-git-fetch>> for details.
371
372You might want to build on one of these remote-tracking branches
373on a branch of your own, just as you would for a tag:
Junio C Hamano8f62db92007-02-01 00:22:22374
375------------------------------------------------
376$ git checkout -b my-todo-copy origin/todo
377------------------------------------------------
378
Junio C Hamano947ab822013-03-19 23:07:29379You can also check out `origin/todo` directly to examine it or
Junio C Hamano97bcb482010-11-25 03:16:07380write a one-off patch. See <<detached-head,detached head>>.
381
Junio C Hamano076ffcc2013-02-06 05:13:21382Note that the name "origin" is just the name that Git uses by default
Junio C Hamano8f62db92007-02-01 00:22:22383to refer to the repository that you cloned from.
384
385[[how-git-stores-references]]
386Naming branches, tags, and other references
387-------------------------------------------
388
389Branches, remote-tracking branches, and tags are all references to
390commits. All references are named with a slash-separated path name
Junio C Hamano947ab822013-03-19 23:07:29391starting with `refs`; the names we've been using so far are actually
Junio C Hamano8f62db92007-02-01 00:22:22392shorthand:
393
Junio C Hamano947ab822013-03-19 23:07:29394- The branch `test` is short for `refs/heads/test`.
395- The tag `v2.6.18` is short for `refs/tags/v2.6.18`.
396- `origin/master` is short for `refs/remotes/origin/master`.
Junio C Hamano8f62db92007-02-01 00:22:22397
398The full name is occasionally useful if, for example, there ever
399exists a tag and a branch with the same name.
400
Junio C Hamano947ab822013-03-19 23:07:29401(Newly created refs are actually stored in the `.git/refs` directory,
Junio C Hamano9810d632007-09-24 01:05:34402under the path given by their name. However, for efficiency reasons
403they may also be packed together in a single file; see
Junio C Hamano35738e82008-01-07 07:55:46404linkgit:git-pack-refs[1]).
Junio C Hamano9810d632007-09-24 01:05:34405
Junio C Hamano3d30fd52007-05-08 00:32:53406As another useful shortcut, the "HEAD" of a repository can be referred
407to just using the name of that repository. So, for example, "origin"
408is usually a shortcut for the HEAD branch in the repository "origin".
Junio C Hamano8f62db92007-02-01 00:22:22409
Junio C Hamano076ffcc2013-02-06 05:13:21410For the complete list of paths which Git checks for references, and
Junio C Hamano8f62db92007-02-01 00:22:22411the order it uses to decide which to choose when there are multiple
412references with the same shorthand name, see the "SPECIFYING
Junio C Hamanoc27b7332010-10-14 04:37:28413REVISIONS" section of linkgit:gitrevisions[7].
Junio C Hamano8f62db92007-02-01 00:22:22414
Junio C Hamanoec87f522008-12-10 08:35:25415[[Updating-a-repository-With-git-fetch]]
Junio C Hamano5f9a6f02009-04-06 08:26:56416Updating a repository with git fetch
Junio C Hamano8f62db92007-02-01 00:22:22417------------------------------------
418
Junio C Hamanoc8c398a2014-06-16 21:14:05419After you clone a repository and commit a few changes of your own, you
420may wish to check the original repository for updates.
Junio C Hamano8f62db92007-02-01 00:22:22421
Junio C Hamanoc8c398a2014-06-16 21:14:05422The `git-fetch` command, with no arguments, will update all of the
423remote-tracking branches to the latest version found in the original
Junio C Hamano8f62db92007-02-01 00:22:22424repository. It will not touch any of your own branches--not even the
425"master" branch that was created for you on clone.
426
Junio C Hamano3d30fd52007-05-08 00:32:53427[[fetching-branches]]
Junio C Hamano8f62db92007-02-01 00:22:22428Fetching branches from other repositories
429-----------------------------------------
430
431You can also track branches from repositories other than the one you
Junio C Hamano35738e82008-01-07 07:55:46432cloned from, using linkgit:git-remote[1]:
Junio C Hamano8f62db92007-02-01 00:22:22433
434-------------------------------------------------
Junio C Hamanoa1952302013-07-01 21:31:18435$ git remote add staging git://git.kernel.org/.../gregkh/staging.git
436$ git fetch staging
437...
438From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
439 * [new branch] master -> staging/master
440 * [new branch] staging-linus -> staging/staging-linus
441 * [new branch] staging-next -> staging/staging-next
Junio C Hamano8f62db92007-02-01 00:22:22442-------------------------------------------------
443
444New remote-tracking branches will be stored under the shorthand name
Junio C Hamanoa1952302013-07-01 21:31:18445that you gave `git remote add`, in this case `staging`:
Junio C Hamano8f62db92007-02-01 00:22:22446
447-------------------------------------------------
448$ git branch -r
Junio C Hamanoa1952302013-07-01 21:31:18449 origin/HEAD -> origin/master
450 origin/master
451 staging/master
452 staging/staging-linus
453 staging/staging-next
Junio C Hamano8f62db92007-02-01 00:22:22454-------------------------------------------------
455
Junio C Hamano947ab822013-03-19 23:07:29456If you run `git fetch <remote>` later, the remote-tracking branches
457for the named `<remote>` will be updated.
Junio C Hamano8f62db92007-02-01 00:22:22458
Junio C Hamano947ab822013-03-19 23:07:29459If you examine the file `.git/config`, you will see that Git has added
Junio C Hamano8f62db92007-02-01 00:22:22460a new stanza:
461
462-------------------------------------------------
463$ cat .git/config
464...
Junio C Hamanoa1952302013-07-01 21:31:18465[remote "staging"]
466url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
467fetch = +refs/heads/*:refs/remotes/staging/*
Junio C Hamano8f62db92007-02-01 00:22:22468...
469-------------------------------------------------
470
Junio C Hamano076ffcc2013-02-06 05:13:21471This is what causes Git to track the remote's branches; you may modify
Junio C Hamano947ab822013-03-19 23:07:29472or delete these configuration options by editing `.git/config` with a
Junio C Hamano8f62db92007-02-01 00:22:22473text editor. (See the "CONFIGURATION FILE" section of
Junio C Hamano35738e82008-01-07 07:55:46474linkgit:git-config[1] for details.)
Junio C Hamano8f62db92007-02-01 00:22:22475
Junio C Hamano3d30fd52007-05-08 00:32:53476[[exploring-git-history]]
Junio C Hamano076ffcc2013-02-06 05:13:21477Exploring Git history
Junio C Hamano8f62db92007-02-01 00:22:22478=====================
479
480Git is best thought of as a tool for storing the history of a
481collection of files. It does this by storing compressed snapshots of
Junio C Hamanocc13f552007-07-24 08:59:43482the contents of a file hierarchy, together with "commits" which show
Junio C Hamano8f62db92007-02-01 00:22:22483the relationships between these snapshots.
484
485Git provides extremely flexible and fast tools for exploring the
486history of a project.
487
Junio C Hamano39381a72007-02-02 07:35:15488We start with one specialized tool that is useful for finding the
Junio C Hamano8f62db92007-02-01 00:22:22489commit that introduced a bug into a project.
490
Junio C Hamano3d30fd52007-05-08 00:32:53491[[using-bisect]]
Junio C Hamano8f62db92007-02-01 00:22:22492How to use bisect to find a regression
493--------------------------------------
494
495Suppose version 2.6.18 of your project worked, but the version at
496"master" crashes. Sometimes the best way to find the cause of such a
497regression is to perform a brute-force search through the project's
498history to find the particular commit that caused the problem. The
Junio C Hamano35738e82008-01-07 07:55:46499linkgit:git-bisect[1] command can help you do this:
Junio C Hamano8f62db92007-02-01 00:22:22500
501-------------------------------------------------
502$ git bisect start
503$ git bisect good v2.6.18
504$ git bisect bad master
505Bisecting: 3537 revisions left to test after this
506[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]
507-------------------------------------------------
508
Junio C Hamano947ab822013-03-19 23:07:29509If you run `git branch` at this point, you'll see that Git has
Junio C Hamano9e395072008-07-31 22:11:21510temporarily moved you in "(no branch)". HEAD is now detached from any
511branch and points directly to a commit (with commit id 65934...) that
512is reachable from "master" but not from v2.6.18. Compile and test it,
513and see whether it crashes. Assume it does crash. Then:
Junio C Hamano8f62db92007-02-01 00:22:22514
515-------------------------------------------------
516$ git bisect bad
517Bisecting: 1769 revisions left to test after this
518[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
519-------------------------------------------------
520
Junio C Hamano076ffcc2013-02-06 05:13:21521checks out an older version. Continue like this, telling Git at each
Junio C Hamano8f62db92007-02-01 00:22:22522stage whether the version it gives you is good or bad, and notice
523that the number of revisions left to test is cut approximately in
524half each time.
525
526After about 13 tests (in this case), it will output the commit id of
527the guilty commit. You can then examine the commit with
Junio C Hamano35738e82008-01-07 07:55:46528linkgit:git-show[1], find out who wrote it, and mail them your bug
Junio C Hamano8f62db92007-02-01 00:22:22529report with the commit id. Finally, run
530
531-------------------------------------------------
532$ git bisect reset
533-------------------------------------------------
534
Junio C Hamano9e395072008-07-31 22:11:21535to return you to the branch you were on before.
Junio C Hamano8f62db92007-02-01 00:22:22536
Junio C Hamano5f9a6f02009-04-06 08:26:56537Note that the version which `git bisect` checks out for you at each
Junio C Hamano8f62db92007-02-01 00:22:22538point is just a suggestion, and you're free to try a different
539version if you think it would be a good idea. For example,
540occasionally you may land on a commit that broke something unrelated;
541run
542
543-------------------------------------------------
Junio C Hamano4c6aa8a2007-04-04 08:56:37544$ git bisect visualize
Junio C Hamano8f62db92007-02-01 00:22:22545-------------------------------------------------
546
547which will run gitk and label the commit it chose with a marker that
Junio C Hamanod32738e2008-07-09 19:53:42548says "bisect". Choose a safe-looking commit nearby, note its commit
Junio C Hamano8f62db92007-02-01 00:22:22549id, and check it out with:
550
551-------------------------------------------------
552$ git reset --hard fb47ddb2db...
553-------------------------------------------------
554
Junio C Hamano947ab822013-03-19 23:07:29555then test, run `bisect good` or `bisect bad` as appropriate, and
Junio C Hamano8f62db92007-02-01 00:22:22556continue.
557
Junio C Hamano947ab822013-03-19 23:07:29558Instead of `git bisect visualize` and then `git reset --hard
559fb47ddb2db...`, you might just want to tell Git that you want to skip
Junio C Hamano9e395072008-07-31 22:11:21560the current commit:
561
562-------------------------------------------------
563$ git bisect skip
564-------------------------------------------------
565
Junio C Hamano076ffcc2013-02-06 05:13:21566In this case, though, Git may not eventually be able to tell the first
Junio C Hamano610d1762008-11-28 06:27:13567bad one between some first skipped commits and a later bad commit.
Junio C Hamano9e395072008-07-31 22:11:21568
569There are also ways to automate the bisecting process if you have a
570test script that can tell a good from a bad commit. See
Junio C Hamano947ab822013-03-19 23:07:29571linkgit:git-bisect[1] for more information about this and other `git
572bisect` features.
Junio C Hamano9e395072008-07-31 22:11:21573
Junio C Hamano3d30fd52007-05-08 00:32:53574[[naming-commits]]
Junio C Hamano8f62db92007-02-01 00:22:22575Naming commits
576--------------
577
578We have seen several ways of naming commits already:
579
580- 40-hexdigit object name
581- branch name: refers to the commit at the head of the given
582 branch
583- tag name: refers to the commit pointed to by the given tag
584 (we've seen branches and tags are special cases of
585 <<how-git-stores-references,references>>).
586- HEAD: refers to the head of the current branch
587
588There are many more; see the "SPECIFYING REVISIONS" section of the
Junio C Hamanoc27b7332010-10-14 04:37:28589linkgit:gitrevisions[7] man page for the complete list of ways to
Junio C Hamano8f62db92007-02-01 00:22:22590name revisions. Some examples:
591
592-------------------------------------------------
593$ git show fb47ddb2 # the first few characters of the object name
594 # are usually enough to specify it uniquely
595$ git show HEAD^ # the parent of the HEAD commit
596$ git show HEAD^^ # the grandparent
597$ git show HEAD~4 # the great-great-grandparent
598-------------------------------------------------
599
600Recall that merge commits may have more than one parent; by default,
Junio C Hamano947ab822013-03-19 23:07:29601`^` and `~` follow the first parent listed in the commit, but you can
Junio C Hamano8f62db92007-02-01 00:22:22602also choose:
603
604-------------------------------------------------
605$ git show HEAD^1 # show the first parent of HEAD
606$ git show HEAD^2 # show the second parent of HEAD
607-------------------------------------------------
608
609In addition to HEAD, there are several other special names for
610commits:
611
612Merges (to be discussed later), as well as operations such as
Junio C Hamano5f9a6f02009-04-06 08:26:56613`git reset`, which change the currently checked-out commit, generally
Junio C Hamano8f62db92007-02-01 00:22:22614set ORIG_HEAD to the value HEAD had before the current operation.
615
Junio C Hamano5f9a6f02009-04-06 08:26:56616The `git fetch` operation always stores the head of the last fetched
617branch in FETCH_HEAD. For example, if you run `git fetch` without
Junio C Hamano8f62db92007-02-01 00:22:22618specifying a local branch as the target of the operation
619
620-------------------------------------------------
621$ git fetch git://example.com/proj.git theirbranch
622-------------------------------------------------
623
624the fetched commits will still be available from FETCH_HEAD.
625
626When we discuss merges we'll also see the special name MERGE_HEAD,
627which refers to the other branch that we're merging in to the current
628branch.
629
Junio C Hamano35738e82008-01-07 07:55:46630The linkgit:git-rev-parse[1] command is a low-level command that is
Junio C Hamano8f62db92007-02-01 00:22:22631occasionally useful for translating some name for a commit to the object
632name for that commit:
633
634-------------------------------------------------
635$ git rev-parse origin
636e05db0fd4f31dde7005f075a84f96b360d05984b
637-------------------------------------------------
638
Junio C Hamano3d30fd52007-05-08 00:32:53639[[creating-tags]]
Junio C Hamano8f62db92007-02-01 00:22:22640Creating tags
641-------------
642
643We can also create a tag to refer to a particular commit; after
644running
645
646-------------------------------------------------
Junio C Hamano4c6aa8a2007-04-04 08:56:37647$ git tag stable-1 1b2e1d63ff
Junio C Hamano8f62db92007-02-01 00:22:22648-------------------------------------------------
649
Junio C Hamano947ab822013-03-19 23:07:29650You can use `stable-1` to refer to the commit 1b2e1d63ff.
Junio C Hamano8f62db92007-02-01 00:22:22651
Junio C Hamano3d30fd52007-05-08 00:32:53652This creates a "lightweight" tag. If you would also like to include a
653comment with the tag, and possibly sign it cryptographically, then you
Junio C Hamano35738e82008-01-07 07:55:46654should create a tag object instead; see the linkgit:git-tag[1] man page
Junio C Hamano3d30fd52007-05-08 00:32:53655for details.
Junio C Hamano8f62db92007-02-01 00:22:22656
Junio C Hamano3d30fd52007-05-08 00:32:53657[[browsing-revisions]]
Junio C Hamano8f62db92007-02-01 00:22:22658Browsing revisions
659------------------
660
Junio C Hamano35738e82008-01-07 07:55:46661The linkgit:git-log[1] command can show lists of commits. On its
Junio C Hamano8f62db92007-02-01 00:22:22662own, it shows all commits reachable from the parent commit; but you
663can also make more specific requests:
664
665-------------------------------------------------
666$ git log v2.5.. # commits since (not reachable from) v2.5
667$ git log test..master # commits reachable from master but not test
668$ git log master..test # ...reachable from test but not master
669$ git log master...test # ...reachable from either test or master,
670# but not both
671$ git log --since="2 weeks ago" # commits from the last 2 weeks
672$ git log Makefile # commits which modify Makefile
673$ git log fs/ # ... which modify any file under fs/
674$ git log -S'foo()' # commits which add or remove any file data
675# matching the string 'foo()'
676-------------------------------------------------
677
678And of course you can combine all of these; the following finds
Junio C Hamano947ab822013-03-19 23:07:29679commits since v2.5 which touch the `Makefile` or any file under `fs`:
Junio C Hamano8f62db92007-02-01 00:22:22680
681-------------------------------------------------
682$ git log v2.5.. Makefile fs/
683-------------------------------------------------
684
685You can also ask git log to show patches:
686
687-------------------------------------------------
688$ git log -p
689-------------------------------------------------
690
Junio C Hamano947ab822013-03-19 23:07:29691See the `--pretty` option in the linkgit:git-log[1] man page for more
Junio C Hamano8f62db92007-02-01 00:22:22692display options.
693
694Note that git log starts with the most recent commit and works
Junio C Hamano076ffcc2013-02-06 05:13:21695backwards through the parents; however, since Git history can contain
Junio C Hamanoee1e4282007-02-04 08:32:04696multiple independent lines of development, the particular order that
Junio C Hamano8f62db92007-02-01 00:22:22697commits are listed in may be somewhat arbitrary.
698
Junio C Hamano3d30fd52007-05-08 00:32:53699[[generating-diffs]]
Junio C Hamano8f62db92007-02-01 00:22:22700Generating diffs
701----------------
702
703You can generate diffs between any two versions using
Junio C Hamano35738e82008-01-07 07:55:46704linkgit:git-diff[1]:
Junio C Hamano8f62db92007-02-01 00:22:22705
706-------------------------------------------------
707$ git diff master..test
708-------------------------------------------------
709
Junio C Hamano393e57f2007-11-20 04:53:25710That will produce the diff between the tips of the two branches. If
711you'd prefer to find the diff from their common ancestor to test, you
712can use three dots instead of two:
713
714-------------------------------------------------
715$ git diff master...test
716-------------------------------------------------
717
718Sometimes what you want instead is a set of patches; for this you can
Junio C Hamano35738e82008-01-07 07:55:46719use linkgit:git-format-patch[1]:
Junio C Hamano8f62db92007-02-01 00:22:22720
721-------------------------------------------------
722$ git format-patch master..test
723-------------------------------------------------
724
725will generate a file with a patch for each commit reachable from test
Junio C Hamano393e57f2007-11-20 04:53:25726but not from master.
Junio C Hamano8f62db92007-02-01 00:22:22727
Junio C Hamano3d30fd52007-05-08 00:32:53728[[viewing-old-file-versions]]
Junio C Hamano8f62db92007-02-01 00:22:22729Viewing old file versions
730-------------------------
731
732You can always view an old version of a file by just checking out the
733correct revision first. But sometimes it is more convenient to be
734able to view an old version of a single file without checking
735anything out; this command does that:
736
737-------------------------------------------------
738$ git show v2.5:fs/locks.c
739-------------------------------------------------
740
741Before the colon may be anything that names a commit, and after it
Junio C Hamano076ffcc2013-02-06 05:13:21742may be any path to a file tracked by Git.
Junio C Hamano8f62db92007-02-01 00:22:22743
Junio C Hamano3d30fd52007-05-08 00:32:53744[[history-examples]]
Junio C Hamano8f62db92007-02-01 00:22:22745Examples
746--------
747
Junio C Hamano75485c82007-05-19 04:20:33748[[counting-commits-on-a-branch]]
749Counting the number of commits on a branch
750~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
751
Junio C Hamano947ab822013-03-19 23:07:29752Suppose you want to know how many commits you've made on `mybranch`
753since it diverged from `origin`:
Junio C Hamano75485c82007-05-19 04:20:33754
755-------------------------------------------------
756$ git log --pretty=oneline origin..mybranch | wc -l
757-------------------------------------------------
758
759Alternatively, you may often see this sort of thing done with the
Junio C Hamano5f9a6f02009-04-06 08:26:56760lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's
Junio C Hamano75485c82007-05-19 04:20:33761of all the given commits:
762
763-------------------------------------------------
764$ git rev-list origin..mybranch | wc -l
765-------------------------------------------------
766
Junio C Hamano3d30fd52007-05-08 00:32:53767[[checking-for-equal-branches]]
Junio C Hamano8f62db92007-02-01 00:22:22768Check whether two branches point at the same history
769~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
770
771Suppose you want to check whether two branches point at the same point
772in history.
773
774-------------------------------------------------
775$ git diff origin..master
776-------------------------------------------------
777
778will tell you whether the contents of the project are the same at the
779two branches; in theory, however, it's possible that the same project
780contents could have been arrived at by two different historical
781routes. You could compare the object names:
782
783-------------------------------------------------
784$ git rev-list origin
785e05db0fd4f31dde7005f075a84f96b360d05984b
786$ git rev-list master
787e05db0fd4f31dde7005f075a84f96b360d05984b
788-------------------------------------------------
789
Junio C Hamano947ab822013-03-19 23:07:29790Or you could recall that the `...` operator selects all commits
Junio C Hamanoe6f28d02013-09-17 21:34:00791reachable from either one reference or the other but not
Junio C Hamano8c5696d2013-02-11 05:35:00792both; so
Junio C Hamano8f62db92007-02-01 00:22:22793
794-------------------------------------------------
795$ git log origin...master
796-------------------------------------------------
797
798will return no commits when the two branches are equal.
799
Junio C Hamano3d30fd52007-05-08 00:32:53800[[finding-tagged-descendants]]
Junio C Hamano8f62db92007-02-01 00:22:22801Find first tagged version including a given fix
802~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
803
804Suppose you know that the commit e05db0fd fixed a certain problem.
805You'd like to find the earliest tagged release that contains that
806fix.
807
808Of course, there may be more than one answer--if the history branched
809after commit e05db0fd, then there could be multiple "earliest" tagged
810releases.
811
812You could just visually inspect the commits since e05db0fd:
813
814-------------------------------------------------
815$ gitk e05db0fd..
816-------------------------------------------------
817
Junio C Hamanoe6f28d02013-09-17 21:34:00818or you can use linkgit:git-name-rev[1], which will give the commit a
Junio C Hamano8f62db92007-02-01 00:22:22819name based on any tag it finds pointing to one of the commit's
820descendants:
821
822-------------------------------------------------
Junio C Hamano4c6aa8a2007-04-04 08:56:37823$ git name-rev --tags e05db0fd
Junio C Hamano8f62db92007-02-01 00:22:22824e05db0fd tags/v1.5.0-rc1^0~23
825-------------------------------------------------
826
Junio C Hamano35738e82008-01-07 07:55:46827The linkgit:git-describe[1] command does the opposite, naming the
Junio C Hamano8f62db92007-02-01 00:22:22828revision using a tag on which the given commit is based:
829
830-------------------------------------------------
831$ git describe e05db0fd
Junio C Hamano4c6aa8a2007-04-04 08:56:37832v1.5.0-rc0-260-ge05db0f
Junio C Hamano8f62db92007-02-01 00:22:22833-------------------------------------------------
834
835but that may sometimes help you guess which tags might come after the
836given commit.
837
838If you just want to verify whether a given tagged version contains a
Junio C Hamano35738e82008-01-07 07:55:46839given commit, you could use linkgit:git-merge-base[1]:
Junio C Hamano8f62db92007-02-01 00:22:22840
841-------------------------------------------------
842$ git merge-base e05db0fd v1.5.0-rc1
843e05db0fd4f31dde7005f075a84f96b360d05984b
844-------------------------------------------------
845
846The merge-base command finds a common ancestor of the given commits,
847and always returns one or the other in the case where one is a
848descendant of the other; so the above output shows that e05db0fd
849actually is an ancestor of v1.5.0-rc1.
850
851Alternatively, note that
852
853-------------------------------------------------
854$ git log v1.5.0-rc1..e05db0fd
855-------------------------------------------------
856
857will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
858because it outputs only commits that are not reachable from v1.5.0-rc1.
859
Junio C Hamano35738e82008-01-07 07:55:46860As yet another alternative, the linkgit:git-show-branch[1] command lists
Junio C Hamano8f62db92007-02-01 00:22:22861the commits reachable from its arguments with a display on the left-hand
Junio C Hamanoe6f28d02013-09-17 21:34:00862side that indicates which arguments that commit is reachable from.
863So, if you run something like
Junio C Hamano8f62db92007-02-01 00:22:22864
865-------------------------------------------------
866$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
867! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
868available
869 ! [v1.5.0-rc0] GIT v1.5.0 preview
870 ! [v1.5.0-rc1] GIT v1.5.0-rc1
871 ! [v1.5.0-rc2] GIT v1.5.0-rc2
872...
873-------------------------------------------------
874
Junio C Hamanoe6f28d02013-09-17 21:34:00875then a line like
Junio C Hamano8f62db92007-02-01 00:22:22876
877-------------------------------------------------
878+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
879available
880-------------------------------------------------
881
Junio C Hamanoe6f28d02013-09-17 21:34:00882shows that e05db0fd is reachable from itself, from v1.5.0-rc1,
883and from v1.5.0-rc2, and not from v1.5.0-rc0.
Junio C Hamano8f62db92007-02-01 00:22:22884
Junio C Hamano75485c82007-05-19 04:20:33885[[showing-commits-unique-to-a-branch]]
886Showing commits unique to a given branch
887~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
888
889Suppose you would like to see all the commits reachable from the branch
Junio C Hamano947ab822013-03-19 23:07:29890head named `master` but not from any other head in your repository.
Junio C Hamano75485c82007-05-19 04:20:33891
892We can list all the heads in this repository with
Junio C Hamano35738e82008-01-07 07:55:46893linkgit:git-show-ref[1]:
Junio C Hamano75485c82007-05-19 04:20:33894
895-------------------------------------------------
896$ git show-ref --heads
897bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial
898db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint
899a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master
90024dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2
9011e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes
902-------------------------------------------------
903
Junio C Hamano947ab822013-03-19 23:07:29904We can get just the branch-head names, and remove `master`, with
Junio C Hamano75485c82007-05-19 04:20:33905the help of the standard utilities cut and grep:
906
907-------------------------------------------------
908$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'
909refs/heads/core-tutorial
910refs/heads/maint
911refs/heads/tutorial-2
912refs/heads/tutorial-fixes
913-------------------------------------------------
914
915And then we can ask to see all the commits reachable from master
916but not from these other heads:
917
918-------------------------------------------------
919$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |
920grep -v '^refs/heads/master' )
921-------------------------------------------------
922
923Obviously, endless variations are possible; for example, to see all
924commits reachable from some head but not from any tag in the repository:
925
926-------------------------------------------------
Junio C Hamano591dc6a2007-05-29 09:18:19927$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )
Junio C Hamano75485c82007-05-19 04:20:33928-------------------------------------------------
929
Junio C Hamanoc27b7332010-10-14 04:37:28930(See linkgit:gitrevisions[7] for explanations of commit-selecting
Junio C Hamano75485c82007-05-19 04:20:33931syntax such as `--not`.)
932
933[[making-a-release]]
934Creating a changelog and tarball for a software release
935~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
936
Junio C Hamano35738e82008-01-07 07:55:46937The linkgit:git-archive[1] command can create a tar or zip archive from
Junio C Hamano75485c82007-05-19 04:20:33938any version of a project; for example:
939
940-------------------------------------------------
Junio C Hamano2da4ac42013-02-19 00:41:17941$ git archive -o latest.tar.gz --prefix=project/ HEAD
Junio C Hamano75485c82007-05-19 04:20:33942-------------------------------------------------
943
Junio C Hamano2da4ac42013-02-19 00:41:17944will use HEAD to produce a gzipped tar archive in which each filename
945is preceded by `project/`. The output file format is inferred from
946the output file extension if possible, see linkgit:git-archive[1] for
947details.
948
Junio C Hamano947ab822013-03-19 23:07:29949Versions of Git older than 1.7.7 don't know about the `tar.gz` format,
Junio C Hamano2da4ac42013-02-19 00:41:17950you'll need to use gzip explicitly:
951
952-------------------------------------------------
953$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz
954-------------------------------------------------
Junio C Hamano75485c82007-05-19 04:20:33955
956If you're releasing a new version of a software project, you may want
957to simultaneously make a changelog to include in the release
958announcement.
959
960Linus Torvalds, for example, makes new kernel releases by tagging them,
961then running:
962
963-------------------------------------------------
964$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7
965-------------------------------------------------
966
967where release-script is a shell script that looks like:
968
969-------------------------------------------------
970#!/bin/sh
971stable="$1"
972last="$2"
973new="$3"
974echo "# git tag v$new"
975echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz"
976echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz"
977echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new"
978echo "git shortlog --no-merges v$new ^v$last > ../ShortLog"
979echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new"
980-------------------------------------------------
981
982and then he just cut-and-pastes the output commands after verifying that
983they look OK.
Junio C Hamano8f62db92007-02-01 00:22:22984
Junio C Hamano3b4609d2010-09-30 00:04:34985[[Finding-commits-With-given-Content]]
Junio C Hamanoed7f4f62007-05-20 09:09:09986Finding commits referencing a file with given content
Junio C Hamano8b8b0f22007-08-26 22:10:26987~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamanoed7f4f62007-05-20 09:09:09988
989Somebody hands you a copy of a file, and asks which commits modified a
990file such that it contained the given content either before or after the
991commit. You can find out with this:
992
993-------------------------------------------------
Junio C Hamano764a6672007-10-23 01:23:31994$ git log --raw --abbrev=40 --pretty=oneline |
Junio C Hamanoed7f4f62007-05-20 09:09:09995grep -B 1 `git hash-object filename`
996-------------------------------------------------
997
998Figuring out why this works is left as an exercise to the (advanced)
Junio C Hamano35738e82008-01-07 07:55:46999student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and
1000linkgit:git-hash-object[1] man pages may prove helpful.
Junio C Hamanoed7f4f62007-05-20 09:09:091001
Junio C Hamanoec87f522008-12-10 08:35:251002[[Developing-With-git]]
Junio C Hamano076ffcc2013-02-06 05:13:211003Developing with Git
Junio C Hamano8f62db92007-02-01 00:22:221004===================
1005
Junio C Hamano3d30fd52007-05-08 00:32:531006[[telling-git-your-name]]
Junio C Hamano076ffcc2013-02-06 05:13:211007Telling Git your name
Junio C Hamano8f62db92007-02-01 00:22:221008---------------------
1009
Junio C Hamano2da4ac42013-02-19 00:41:171010Before creating any commits, you should introduce yourself to Git.
1011The easiest way to do so is to use linkgit:git-config[1]:
1012
1013------------------------------------------------
1014$ git config --global user.name 'Your Name Comes Here'
1015$ git config --global user.email 'you@yourdomain.example.com'
1016------------------------------------------------
1017
1018Which will add the following to a file named `.gitconfig` in your
1019home directory:
Junio C Hamano8f62db92007-02-01 00:22:221020
1021------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:221022[user]
1023name = Your Name Comes Here
1024email = you@yourdomain.example.com
Junio C Hamano8f62db92007-02-01 00:22:221025------------------------------------------------
1026
Junio C Hamano2da4ac42013-02-19 00:41:171027See the "CONFIGURATION FILE" section of linkgit:git-config[1] for
1028details on the configuration file. The file is plain text, so you can
1029also edit it with your favorite editor.
Junio C Hamano8f62db92007-02-01 00:22:221030
1031
Junio C Hamano3d30fd52007-05-08 00:32:531032[[creating-a-new-repository]]
Junio C Hamano8f62db92007-02-01 00:22:221033Creating a new repository
1034-------------------------
1035
1036Creating a new repository from scratch is very easy:
1037
1038-------------------------------------------------
1039$ mkdir project
1040$ cd project
1041$ git init
1042-------------------------------------------------
1043
1044If you have some initial content (say, a tarball):
1045
1046-------------------------------------------------
Junio C Hamano4fbdd442009-01-06 05:56:241047$ tar xzvf project.tar.gz
Junio C Hamano8f62db92007-02-01 00:22:221048$ cd project
1049$ git init
1050$ git add . # include everything below ./ in the first commit:
1051$ git commit
1052-------------------------------------------------
1053
1054[[how-to-make-a-commit]]
Junio C Hamano12a3a232007-04-07 10:18:101055How to make a commit
Junio C Hamano8f62db92007-02-01 00:22:221056--------------------
1057
1058Creating a new commit takes three steps:
1059
10601. Making some changes to the working directory using your
1061 favorite editor.
Junio C Hamano076ffcc2013-02-06 05:13:2110622. Telling Git about your changes.
10633. Creating the commit using the content you told Git about
Junio C Hamano8f62db92007-02-01 00:22:221064 in step 2.
1065
1066In practice, you can interleave and repeat steps 1 and 2 as many
1067times as you want: in order to keep track of what you want committed
Junio C Hamano076ffcc2013-02-06 05:13:211068at step 3, Git maintains a snapshot of the tree's contents in a
Junio C Hamano8f62db92007-02-01 00:22:221069special staging area called "the index."
1070
1071At the beginning, the content of the index will be identical to
Junio C Hamano947ab822013-03-19 23:07:291072that of the HEAD. The command `git diff --cached`, which shows
Junio C Hamano8f62db92007-02-01 00:22:221073the difference between the HEAD and the index, should therefore
1074produce no output at that point.
1075
1076Modifying the index is easy:
1077
Junio C Hamanoe6f28d02013-09-17 21:34:001078To update the index with the contents of a new or modified file, use
Junio C Hamano8f62db92007-02-01 00:22:221079
1080-------------------------------------------------
1081$ git add path/to/file
1082-------------------------------------------------
1083
Junio C Hamanoe6f28d02013-09-17 21:34:001084To remove a file from the index and from the working tree, use
Junio C Hamano8f62db92007-02-01 00:22:221085
1086-------------------------------------------------
1087$ git rm path/to/file
1088-------------------------------------------------
1089
1090After each step you can verify that
1091
1092-------------------------------------------------
1093$ git diff --cached
1094-------------------------------------------------
1095
1096always shows the difference between the HEAD and the index file--this
1097is what you'd commit if you created the commit now--and that
1098
1099-------------------------------------------------
1100$ git diff
1101-------------------------------------------------
1102
1103shows the difference between the working tree and the index file.
1104
Junio C Hamano947ab822013-03-19 23:07:291105Note that `git add` always adds just the current contents of a file
Junio C Hamano8f62db92007-02-01 00:22:221106to the index; further changes to the same file will be ignored unless
Junio C Hamano5f9a6f02009-04-06 08:26:561107you run `git add` on the file again.
Junio C Hamano8f62db92007-02-01 00:22:221108
1109When you're ready, just run
1110
1111-------------------------------------------------
1112$ git commit
1113-------------------------------------------------
1114
Junio C Hamano076ffcc2013-02-06 05:13:211115and Git will prompt you for a commit message and then create the new
Junio C Hamanoee1e4282007-02-04 08:32:041116commit. Check to make sure it looks like what you expected with
Junio C Hamano8f62db92007-02-01 00:22:221117
1118-------------------------------------------------
1119$ git show
1120-------------------------------------------------
1121
1122As a special shortcut,
Junio C Hamanoa77a5132007-06-08 16:13:441123
Junio C Hamano8f62db92007-02-01 00:22:221124-------------------------------------------------
1125$ git commit -a
1126-------------------------------------------------
1127
1128will update the index with any files that you've modified or removed
1129and create a commit, all in one step.
1130
1131A number of commands are useful for keeping track of what you're
1132about to commit:
1133
1134-------------------------------------------------
1135$ git diff --cached # difference between HEAD and the index; what
Junio C Hamanocc13f552007-07-24 08:59:431136 # would be committed if you ran "commit" now.
Junio C Hamano8f62db92007-02-01 00:22:221137$ git diff # difference between the index file and your
1138 # working directory; changes that would not
1139 # be included if you ran "commit" now.
Junio C Hamano3d30fd52007-05-08 00:32:531140$ git diff HEAD # difference between HEAD and working tree; what
1141 # would be committed if you ran "commit -a" now.
Junio C Hamano8f62db92007-02-01 00:22:221142$ git status # a brief per-file summary of the above.
1143-------------------------------------------------
1144
Junio C Hamano35738e82008-01-07 07:55:461145You can also use linkgit:git-gui[1] to create commits, view changes in
Junio C Hamano4cd1c0e2007-08-06 04:39:141146the index and the working tree files, and individually select diff hunks
1147for inclusion in the index (by right-clicking on the diff hunk and
1148choosing "Stage Hunk For Commit").
1149
Junio C Hamano3d30fd52007-05-08 00:32:531150[[creating-good-commit-messages]]
Junio C Hamano12a3a232007-04-07 10:18:101151Creating good commit messages
Junio C Hamano8f62db92007-02-01 00:22:221152-----------------------------
1153
1154Though not required, it's a good idea to begin the commit message
1155with a single short (less than 50 character) line summarizing the
1156change, followed by a blank line and then a more thorough
Junio C Hamano281fd392012-09-17 23:57:411157description. The text up to the first blank line in a commit
1158message is treated as the commit title, and that title is used
Junio C Hamano076ffcc2013-02-06 05:13:211159throughout Git. For example, linkgit:git-format-patch[1] turns a
Junio C Hamano281fd392012-09-17 23:57:411160commit into email, and it uses the title on the Subject line and the
1161rest of the commit in the body.
1162
Junio C Hamano8f62db92007-02-01 00:22:221163
Junio C Hamanoed7f4f62007-05-20 09:09:091164[[ignoring-files]]
1165Ignoring files
1166--------------
1167
Junio C Hamano076ffcc2013-02-06 05:13:211168A project will often generate files that you do 'not' want to track with Git.
Junio C Hamanoed7f4f62007-05-20 09:09:091169This typically includes files generated by a build process or temporary
Junio C Hamano076ffcc2013-02-06 05:13:211170backup files made by your editor. Of course, 'not' tracking files with Git
Junio C Hamano5f9a6f02009-04-06 08:26:561171is just a matter of 'not' calling `git add` on them. But it quickly becomes
Junio C Hamanoed7f4f62007-05-20 09:09:091172annoying to have these untracked files lying around; e.g. they make
Junio C Hamanoea82cff2009-03-18 01:54:481173`git add .` practically useless, and they keep showing up in the output of
1174`git status`.
Junio C Hamanoed7f4f62007-05-20 09:09:091175
Junio C Hamano947ab822013-03-19 23:07:291176You can tell Git to ignore certain files by creating a file called
1177`.gitignore` in the top level of your working directory, with contents
1178such as:
Junio C Hamanoed7f4f62007-05-20 09:09:091179
1180-------------------------------------------------
1181# Lines starting with '#' are considered comments.
Junio C Hamano8b8b0f22007-08-26 22:10:261182# Ignore any file named foo.txt.
Junio C Hamanoed7f4f62007-05-20 09:09:091183foo.txt
1184# Ignore (generated) html files,
1185*.html
1186# except foo.html which is maintained by hand.
1187!foo.html
1188# Ignore objects and archives.
1189*.[oa]
1190-------------------------------------------------
1191
Junio C Hamano35738e82008-01-07 07:55:461192See linkgit:gitignore[5] for a detailed explanation of the syntax. You can
Junio C Hamano8b8b0f22007-08-26 22:10:261193also place .gitignore files in other directories in your working tree, and they
1194will apply to those directories and their subdirectories. The `.gitignore`
1195files can be added to your repository like any other files (just run `git add
1196.gitignore` and `git commit`, as usual), which is convenient when the exclude
1197patterns (such as patterns matching build output files) would also make sense
1198for other users who clone your repository.
Junio C Hamanoed7f4f62007-05-20 09:09:091199
Junio C Hamano8b8b0f22007-08-26 22:10:261200If you wish the exclude patterns to affect only certain repositories
1201(instead of every repository for a given project), you may instead put
Junio C Hamano947ab822013-03-19 23:07:291202them in a file in your repository named `.git/info/exclude`, or in any
Junio C Hamano322c6242015-03-23 21:32:461203file specified by the `core.excludesFile` configuration variable.
Junio C Hamano947ab822013-03-19 23:07:291204Some Git commands can also take exclude patterns directly on the
1205command line. See linkgit:gitignore[5] for the details.
Junio C Hamanoed7f4f62007-05-20 09:09:091206
Junio C Hamano3d30fd52007-05-08 00:32:531207[[how-to-merge]]
Junio C Hamano12a3a232007-04-07 10:18:101208How to merge
Junio C Hamano8f62db92007-02-01 00:22:221209------------
1210
1211You can rejoin two diverging branches of development using
Junio C Hamano35738e82008-01-07 07:55:461212linkgit:git-merge[1]:
Junio C Hamano8f62db92007-02-01 00:22:221213
1214-------------------------------------------------
1215$ git merge branchname
1216-------------------------------------------------
1217
Junio C Hamano947ab822013-03-19 23:07:291218merges the development in the branch `branchname` into the current
Junio C Hamano5706e0b2009-11-24 10:54:161219branch.
1220
Junio C Hamano947ab822013-03-19 23:07:291221A merge is made by combining the changes made in `branchname` and the
Junio C Hamano5706e0b2009-11-24 10:54:161222changes made up to the latest commit in your current branch since
1223their histories forked. The work tree is overwritten by the result of
1224the merge when this combining is done cleanly, or overwritten by a
1225half-merged results when this combining results in conflicts.
1226Therefore, if you have uncommitted changes touching the same files as
1227the ones impacted by the merge, Git will refuse to proceed. Most of
1228the time, you will want to commit your changes before you can merge,
1229and if you don't, then linkgit:git-stash[1] can take these changes
1230away while you're doing the merge, and reapply them afterwards.
1231
Junio C Hamano167b1382010-01-31 23:04:311232If the changes are independent enough, Git will automatically complete
Junio C Hamano5706e0b2009-11-24 10:54:161233the merge and commit the result (or reuse an existing commit in case
1234of <<fast-forwards,fast-forward>>, see below). On the other hand,
1235if there are conflicts--for example, if the same file is
Junio C Hamano8f62db92007-02-01 00:22:221236modified in two different ways in the remote branch and the local
1237branch--then you are warned; the output may look something like this:
1238
1239-------------------------------------------------
Junio C Hamanoc51fede2007-03-12 07:29:201240$ git merge next
1241 100% (4/4) done
1242Auto-merged file.txt
Junio C Hamano8f62db92007-02-01 00:22:221243CONFLICT (content): Merge conflict in file.txt
1244Automatic merge failed; fix conflicts and then commit the result.
1245-------------------------------------------------
1246
1247Conflict markers are left in the problematic files, and after
1248you resolve the conflicts manually, you can update the index
Junio C Hamano076ffcc2013-02-06 05:13:211249with the contents and run Git commit, as you normally would when
Junio C Hamano8f62db92007-02-01 00:22:221250creating a new file.
1251
1252If you examine the resulting commit using gitk, you will see that it
1253has two parents, one pointing to the top of the current branch, and
1254one to the top of the other branch.
1255
Junio C Hamano8f62db92007-02-01 00:22:221256[[resolving-a-merge]]
1257Resolving a merge
1258-----------------
1259
Junio C Hamano076ffcc2013-02-06 05:13:211260When a merge isn't resolved automatically, Git leaves the index and
Junio C Hamano8f62db92007-02-01 00:22:221261the working tree in a special state that gives you all the
1262information you need to help resolve the merge.
1263
1264Files with conflicts are marked specially in the index, so until you
Junio C Hamano35738e82008-01-07 07:55:461265resolve the problem and update the index, linkgit:git-commit[1] will
Junio C Hamanoaa83a7d2007-03-05 02:37:291266fail:
Junio C Hamano8f62db92007-02-01 00:22:221267
1268-------------------------------------------------
1269$ git commit
1270file.txt: needs merge
1271-------------------------------------------------
1272
Junio C Hamano35738e82008-01-07 07:55:461273Also, linkgit:git-status[1] will list those files as "unmerged", and the
Junio C Hamanoaa83a7d2007-03-05 02:37:291274files with conflicts will have conflict markers added, like this:
1275
1276-------------------------------------------------
1277<<<<<<< HEAD:file.txt
1278Hello world
1279=======
1280Goodbye
1281>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
1282-------------------------------------------------
1283
1284All you need to do is edit the files to resolve the conflicts, and then
1285
1286-------------------------------------------------
1287$ git add file.txt
1288$ git commit
1289-------------------------------------------------
1290
1291Note that the commit message will already be filled in for you with
1292some information about the merge. Normally you can just use this
1293default message unchanged, but you may add additional commentary of
1294your own if desired.
1295
Junio C Hamano076ffcc2013-02-06 05:13:211296The above is all you need to know to resolve a simple merge. But Git
Junio C Hamanoaa83a7d2007-03-05 02:37:291297also provides more information to help resolve conflicts:
1298
Junio C Hamano3d30fd52007-05-08 00:32:531299[[conflict-resolution]]
Junio C Hamanoaa83a7d2007-03-05 02:37:291300Getting conflict-resolution help during a merge
1301~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:221302
Junio C Hamano076ffcc2013-02-06 05:13:211303All of the changes that Git was able to merge automatically are
Junio C Hamano35738e82008-01-07 07:55:461304already added to the index file, so linkgit:git-diff[1] shows only
Junio C Hamanoaa83a7d2007-03-05 02:37:291305the conflicts. It uses an unusual syntax:
Junio C Hamano8f62db92007-02-01 00:22:221306
1307-------------------------------------------------
1308$ git diff
1309diff --cc file.txt
1310index 802992c,2b60207..0000000
1311--- a/file.txt
1312+++ b/file.txt
1313@@@ -1,1 -1,1 +1,5 @@@
1314++<<<<<<< HEAD:file.txt
1315 +Hello world
1316++=======
1317+ Goodbye
1318++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
1319-------------------------------------------------
1320
Junio C Hamanocc13f552007-07-24 08:59:431321Recall that the commit which will be committed after we resolve this
Junio C Hamano8f62db92007-02-01 00:22:221322conflict will have two parents instead of the usual one: one parent
1323will be HEAD, the tip of the current branch; the other will be the
1324tip of the other branch, which is stored temporarily in MERGE_HEAD.
1325
Junio C Hamanoaa83a7d2007-03-05 02:37:291326During the merge, the index holds three versions of each file. Each of
1327these three "file stages" represents a different version of the file:
1328
1329-------------------------------------------------
1330$ git show :1:file.txt # the file in a common ancestor of both branches
Junio C Hamano6fb124c2008-06-13 10:04:011331$ git show :2:file.txt # the version from HEAD.
1332$ git show :3:file.txt # the version from MERGE_HEAD.
Junio C Hamanoaa83a7d2007-03-05 02:37:291333-------------------------------------------------
1334
Junio C Hamano6fb124c2008-06-13 10:04:011335When you ask linkgit:git-diff[1] to show the conflicts, it runs a
1336three-way diff between the conflicted merge results in the work tree with
1337stages 2 and 3 to show only hunks whose contents come from both sides,
1338mixed (in other words, when a hunk's merge results come only from stage 2,
1339that part is not conflicting and is not shown. Same for stage 3).
Junio C Hamanoaa83a7d2007-03-05 02:37:291340
1341The diff above shows the differences between the working-tree version of
1342file.txt and the stage 2 and stage 3 versions. So instead of preceding
Junio C Hamano947ab822013-03-19 23:07:291343each line by a single `+` or `-`, it now uses two columns: the first
Junio C Hamanoaa83a7d2007-03-05 02:37:291344column is used for differences between the first parent and the working
1345directory copy, and the second for differences between the second parent
1346and the working directory copy. (See the "COMBINED DIFF FORMAT" section
Junio C Hamano35738e82008-01-07 07:55:461347of linkgit:git-diff-files[1] for a details of the format.)
Junio C Hamanoaa83a7d2007-03-05 02:37:291348
1349After resolving the conflict in the obvious way (but before updating the
1350index), the diff will look like:
Junio C Hamano8f62db92007-02-01 00:22:221351
1352-------------------------------------------------
1353$ git diff
1354diff --cc file.txt
1355index 802992c,2b60207..0000000
1356--- a/file.txt
1357+++ b/file.txt
1358@@@ -1,1 -1,1 +1,1 @@@
1359- Hello world
1360 -Goodbye
1361++Goodbye world
1362-------------------------------------------------
1363
1364This shows that our resolved version deleted "Hello world" from the
1365first parent, deleted "Goodbye" from the second parent, and added
1366"Goodbye world", which was previously absent from both.
1367
Junio C Hamanoaa83a7d2007-03-05 02:37:291368Some special diff options allow diffing the working directory against
1369any of these stages:
1370
1371-------------------------------------------------
1372$ git diff -1 file.txt # diff against stage 1
1373$ git diff --base file.txt # same as the above
1374$ git diff -2 file.txt # diff against stage 2
1375$ git diff --ours file.txt # same as the above
1376$ git diff -3 file.txt # diff against stage 3
1377$ git diff --theirs file.txt # same as the above.
1378-------------------------------------------------
1379
Junio C Hamanoba4b9282008-07-06 05:20:311380The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help
Junio C Hamanoaa83a7d2007-03-05 02:37:291381for merges:
Junio C Hamano8f62db92007-02-01 00:22:221382
1383-------------------------------------------------
1384$ git log --merge
Junio C Hamanoaa83a7d2007-03-05 02:37:291385$ gitk --merge
Junio C Hamano8f62db92007-02-01 00:22:221386-------------------------------------------------
1387
Junio C Hamanoaa83a7d2007-03-05 02:37:291388These will display all commits which exist only on HEAD or on
1389MERGE_HEAD, and which touch an unmerged file.
Junio C Hamano8f62db92007-02-01 00:22:221390
Junio C Hamano35738e82008-01-07 07:55:461391You may also use linkgit:git-mergetool[1], which lets you merge the
Junio C Hamano4fbdd442009-01-06 05:56:241392unmerged files using external tools such as Emacs or kdiff3.
Junio C Hamano3d30fd52007-05-08 00:32:531393
Junio C Hamanoaa83a7d2007-03-05 02:37:291394Each time you resolve the conflicts in a file and update the index:
Junio C Hamano8f62db92007-02-01 00:22:221395
1396-------------------------------------------------
1397$ git add file.txt
Junio C Hamano8f62db92007-02-01 00:22:221398-------------------------------------------------
1399
Junio C Hamanoaa83a7d2007-03-05 02:37:291400the different stages of that file will be "collapsed", after which
Junio C Hamano5f9a6f02009-04-06 08:26:561401`git diff` will (by default) no longer show diffs for that file.
Junio C Hamano8f62db92007-02-01 00:22:221402
1403[[undoing-a-merge]]
Junio C Hamano12a3a232007-04-07 10:18:101404Undoing a merge
Junio C Hamano8f62db92007-02-01 00:22:221405---------------
1406
1407If you get stuck and decide to just give up and throw the whole mess
1408away, you can always return to the pre-merge state with
1409
1410-------------------------------------------------
1411$ git reset --hard HEAD
1412-------------------------------------------------
1413
Junio C Hamanocc13f552007-07-24 08:59:431414Or, if you've already committed the merge that you want to throw away,
Junio C Hamano8f62db92007-02-01 00:22:221415
1416-------------------------------------------------
Junio C Hamanoaa83a7d2007-03-05 02:37:291417$ git reset --hard ORIG_HEAD
Junio C Hamano8f62db92007-02-01 00:22:221418-------------------------------------------------
1419
1420However, this last command can be dangerous in some cases--never
1421throw away a commit you have already committed if that commit may
1422itself have been merged into another branch, as doing so may confuse
1423further merges.
1424
Junio C Hamano3d30fd52007-05-08 00:32:531425[[fast-forwards]]
Junio C Hamano8f62db92007-02-01 00:22:221426Fast-forward merges
1427-------------------
1428
1429There is one special case not mentioned above, which is treated
1430differently. Normally, a merge results in a merge commit, with two
1431parents, one pointing at each of the two lines of development that
1432were merged.
1433
Junio C Hamano3d30fd52007-05-08 00:32:531434However, if the current branch is a descendant of the other--so every
Junio C Hamano076ffcc2013-02-06 05:13:211435commit present in the one is already contained in the other--then Git
Junio C Hamano3f680f32009-11-16 02:10:541436just performs a "fast-forward"; the head of the current branch is moved
Junio C Hamano3d30fd52007-05-08 00:32:531437forward to point at the head of the merged-in branch, without any new
1438commits being created.
Junio C Hamano8f62db92007-02-01 00:22:221439
Junio C Hamano3d30fd52007-05-08 00:32:531440[[fixing-mistakes]]
Junio C Hamano8f62db92007-02-01 00:22:221441Fixing mistakes
1442---------------
1443
1444If you've messed up the working tree, but haven't yet committed your
1445mistake, you can return the entire working tree to the last committed
1446state with
1447
1448-------------------------------------------------
1449$ git reset --hard HEAD
1450-------------------------------------------------
1451
1452If you make a commit that you later wish you hadn't, there are two
1453fundamentally different ways to fix the problem:
1454
14551. You can create a new commit that undoes whatever was done
Junio C Hamano8c5802d2007-11-15 00:13:361456by the old commit. This is the correct thing if your
Junio C Hamano8f62db92007-02-01 00:22:221457mistake has already been made public.
1458
14592. You can go back and modify the old commit. You should
1460never do this if you have already made the history public;
Junio C Hamano076ffcc2013-02-06 05:13:211461Git does not normally expect the "history" of a project to
Junio C Hamano8f62db92007-02-01 00:22:221462change, and cannot correctly perform repeated merges from
1463a branch that has had its history changed.
1464
Junio C Hamano3d30fd52007-05-08 00:32:531465[[reverting-a-commit]]
Junio C Hamano8f62db92007-02-01 00:22:221466Fixing a mistake with a new commit
1467~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1468
1469Creating a new commit that reverts an earlier change is very easy;
Junio C Hamano35738e82008-01-07 07:55:461470just pass the linkgit:git-revert[1] command a reference to the bad
Junio C Hamano8f62db92007-02-01 00:22:221471commit; for example, to revert the most recent commit:
1472
1473-------------------------------------------------
1474$ git revert HEAD
1475-------------------------------------------------
1476
1477This will create a new commit which undoes the change in HEAD. You
1478will be given a chance to edit the commit message for the new commit.
1479
1480You can also revert an earlier change, for example, the next-to-last:
1481
1482-------------------------------------------------
1483$ git revert HEAD^
1484-------------------------------------------------
1485
Junio C Hamano076ffcc2013-02-06 05:13:211486In this case Git will attempt to undo the old change while leaving
Junio C Hamano8f62db92007-02-01 00:22:221487intact any changes made since then. If more recent changes overlap
1488with the changes to be reverted, then you will be asked to fix
1489conflicts manually, just as in the case of <<resolving-a-merge,
1490resolving a merge>>.
1491
Junio C Hamanoce3650e2007-11-26 04:20:111492[[fixing-a-mistake-by-rewriting-history]]
1493Fixing a mistake by rewriting history
Junio C Hamano8f62db92007-02-01 00:22:221494~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1495
1496If the problematic commit is the most recent commit, and you have not
1497yet made that commit public, then you may just
Junio C Hamano5f9a6f02009-04-06 08:26:561498<<undoing-a-merge,destroy it using `git reset`>>.
Junio C Hamano8f62db92007-02-01 00:22:221499
1500Alternatively, you
1501can edit the working directory and update the index to fix your
1502mistake, just as if you were going to <<how-to-make-a-commit,create a
1503new commit>>, then run
1504
1505-------------------------------------------------
1506$ git commit --amend
1507-------------------------------------------------
1508
1509which will replace the old commit by a new commit incorporating your
1510changes, giving you a chance to edit the old commit message first.
1511
1512Again, you should never do this to a commit that may already have
Junio C Hamano35738e82008-01-07 07:55:461513been merged into another branch; use linkgit:git-revert[1] instead in
Junio C Hamano8f62db92007-02-01 00:22:221514that case.
1515
Junio C Hamanoce3650e2007-11-26 04:20:111516It is also possible to replace commits further back in the history, but
Junio C Hamano8f62db92007-02-01 00:22:221517this is an advanced topic to be left for
1518<<cleaning-up-history,another chapter>>.
1519
Junio C Hamano3d30fd52007-05-08 00:32:531520[[checkout-of-path]]
Junio C Hamano8f62db92007-02-01 00:22:221521Checking out an old version of a file
1522~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1523
1524In the process of undoing a previous bad change, you may find it
1525useful to check out an older version of a particular file using
Junio C Hamano5f9a6f02009-04-06 08:26:561526linkgit:git-checkout[1]. We've used `git checkout` before to switch
Junio C Hamano8f62db92007-02-01 00:22:221527branches, but it has quite different behavior if it is given a path
1528name: the command
1529
1530-------------------------------------------------
1531$ git checkout HEAD^ path/to/file
1532-------------------------------------------------
1533
1534replaces path/to/file by the contents it had in the commit HEAD^, and
1535also updates the index to match. It does not change branches.
1536
1537If you just want to look at an old version of the file, without
1538modifying the working directory, you can do that with
Junio C Hamano35738e82008-01-07 07:55:461539linkgit:git-show[1]:
Junio C Hamano8f62db92007-02-01 00:22:221540
1541-------------------------------------------------
Junio C Hamanoc51fede2007-03-12 07:29:201542$ git show HEAD^:path/to/file
Junio C Hamano8f62db92007-02-01 00:22:221543-------------------------------------------------
1544
1545which will display the given version of the file.
1546
Junio C Hamano4cd1c0e2007-08-06 04:39:141547[[interrupted-work]]
1548Temporarily setting aside work in progress
1549~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1550
1551While you are in the middle of working on something complicated, you
1552find an unrelated but obvious and trivial bug. You would like to fix it
Junio C Hamano35738e82008-01-07 07:55:461553before continuing. You can use linkgit:git-stash[1] to save the current
Junio C Hamano4cd1c0e2007-08-06 04:39:141554state of your work, and after fixing the bug (or, optionally after doing
1555so on a different branch and then coming back), unstash the
1556work-in-progress changes.
1557
1558------------------------------------------------
Junio C Hamano78502452009-02-04 16:53:501559$ git stash save "work in progress for foo feature"
Junio C Hamano4cd1c0e2007-08-06 04:39:141560------------------------------------------------
1561
1562This command will save your changes away to the `stash`, and
1563reset your working tree and the index to match the tip of your
1564current branch. Then you can make your fix as usual.
1565
1566------------------------------------------------
1567... edit and test ...
1568$ git commit -a -m "blorpl: typofix"
1569------------------------------------------------
1570
1571After that, you can go back to what you were working on with
Junio C Hamano7d3275e2009-05-31 21:53:301572`git stash pop`:
Junio C Hamano4cd1c0e2007-08-06 04:39:141573
1574------------------------------------------------
Junio C Hamano7d3275e2009-05-31 21:53:301575$ git stash pop
Junio C Hamano4cd1c0e2007-08-06 04:39:141576------------------------------------------------
1577
1578
Junio C Hamano3d30fd52007-05-08 00:32:531579[[ensuring-good-performance]]
Junio C Hamano8f62db92007-02-01 00:22:221580Ensuring good performance
1581-------------------------
1582
Junio C Hamano076ffcc2013-02-06 05:13:211583On large repositories, Git depends on compression to keep the history
Junio C Hamano8c5696d2013-02-11 05:35:001584information from taking up too much space on disk or in memory. Some
1585Git commands may automatically run linkgit:git-gc[1], so you don't
1586have to worry about running it manually. However, compressing a large
1587repository may take a while, so you may want to call `gc` explicitly
1588to avoid automatic compression kicking in when it is not convenient.
Junio C Hamano8f62db92007-02-01 00:22:221589
Junio C Hamano3d30fd52007-05-08 00:32:531590
1591[[ensuring-reliability]]
Junio C Hamano8f62db92007-02-01 00:22:221592Ensuring reliability
1593--------------------
1594
Junio C Hamano3d30fd52007-05-08 00:32:531595[[checking-for-corruption]]
Junio C Hamano8f62db92007-02-01 00:22:221596Checking the repository for corruption
1597~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1598
Junio C Hamano35738e82008-01-07 07:55:461599The linkgit:git-fsck[1] command runs a number of self-consistency checks
Junio C Hamano8f62db92007-02-01 00:22:221600on the repository, and reports on any problems. This may take some
Junio C Hamano81d540a2012-03-02 19:52:471601time.
Junio C Hamano8f62db92007-02-01 00:22:221602
1603-------------------------------------------------
1604$ git fsck
1605dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1606dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1607dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1608dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
1609dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
1610dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
1611dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
1612dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
1613...
1614-------------------------------------------------
1615
Junio C Hamano81d540a2012-03-02 19:52:471616You will see informational messages on dangling objects. They are objects
1617that still exist in the repository but are no longer referenced by any of
Junio C Hamano947ab822013-03-19 23:07:291618your branches, and can (and will) be removed after a while with `gc`.
Junio C Hamano010705a2012-06-19 23:37:261619You can run `git fsck --no-dangling` to suppress these messages, and still
Junio C Hamano81d540a2012-03-02 19:52:471620view real errors.
Junio C Hamanoce3650e2007-11-26 04:20:111621
Junio C Hamano3d30fd52007-05-08 00:32:531622[[recovering-lost-changes]]
Junio C Hamano8f62db92007-02-01 00:22:221623Recovering lost changes
1624~~~~~~~~~~~~~~~~~~~~~~~
1625
Junio C Hamano3d30fd52007-05-08 00:32:531626[[reflogs]]
Junio C Hamano8f62db92007-02-01 00:22:221627Reflogs
1628^^^^^^^
1629
Junio C Hamano947ab822013-03-19 23:07:291630Say you modify a branch with <<fixing-mistakes,`git reset --hard`>>,
1631and then realize that the branch was the only reference you had to
1632that point in history.
Junio C Hamano8f62db92007-02-01 00:22:221633
Junio C Hamano076ffcc2013-02-06 05:13:211634Fortunately, Git also keeps a log, called a "reflog", of all the
Junio C Hamano8f62db92007-02-01 00:22:221635previous values of each branch. So in this case you can still find the
Junio C Hamanoa77a5132007-06-08 16:13:441636old history using, for example,
Junio C Hamano8f62db92007-02-01 00:22:221637
1638-------------------------------------------------
1639$ git log master@{1}
1640-------------------------------------------------
1641
Junio C Hamano63777e22007-11-17 20:52:161642This lists the commits reachable from the previous version of the
Junio C Hamano947ab822013-03-19 23:07:291643`master` branch head. This syntax can be used with any Git command
1644that accepts a commit, not just with `git log`. Some other examples:
Junio C Hamano8f62db92007-02-01 00:22:221645
1646-------------------------------------------------
1647$ git show master@{2} # See where the branch pointed 2,
1648$ git show master@{3} # 3, ... changes ago.
1649$ gitk master@{yesterday} # See where it pointed yesterday,
1650$ gitk master@{"1 week ago"} # ... or last week
Junio C Hamano3d30fd52007-05-08 00:32:531651$ git log --walk-reflogs master # show reflog entries for master
Junio C Hamano8f62db92007-02-01 00:22:221652-------------------------------------------------
1653
Junio C Hamano3d30fd52007-05-08 00:32:531654A separate reflog is kept for the HEAD, so
1655
1656-------------------------------------------------
1657$ git show HEAD@{"1 week ago"}
1658-------------------------------------------------
1659
1660will show what HEAD pointed to one week ago, not what the current branch
1661pointed to one week ago. This allows you to see the history of what
1662you've checked out.
1663
Junio C Hamano8f62db92007-02-01 00:22:221664The reflogs are kept by default for 30 days, after which they may be
Junio C Hamano35738e82008-01-07 07:55:461665pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn
Junio C Hamano8f62db92007-02-01 00:22:221666how to control this pruning, and see the "SPECIFYING REVISIONS"
Junio C Hamanoc27b7332010-10-14 04:37:281667section of linkgit:gitrevisions[7] for details.
Junio C Hamano8f62db92007-02-01 00:22:221668
Junio C Hamano076ffcc2013-02-06 05:13:211669Note that the reflog history is very different from normal Git history.
Junio C Hamano8f62db92007-02-01 00:22:221670While normal history is shared by every repository that works on the
1671same project, the reflog history is not shared: it tells you only about
1672how the branches in your local repository have changed over time.
1673
Junio C Hamano3d30fd52007-05-08 00:32:531674[[dangling-object-recovery]]
Junio C Hamano8f62db92007-02-01 00:22:221675Examining dangling objects
1676^^^^^^^^^^^^^^^^^^^^^^^^^^
1677
Junio C Hamano3d30fd52007-05-08 00:32:531678In some situations the reflog may not be able to save you. For example,
1679suppose you delete a branch, then realize you need the history it
1680contained. The reflog is also deleted; however, if you have not yet
1681pruned the repository, then you may still be able to find the lost
Junio C Hamano5f9a6f02009-04-06 08:26:561682commits in the dangling objects that `git fsck` reports. See
Junio C Hamano3d30fd52007-05-08 00:32:531683<<dangling-objects>> for the details.
Junio C Hamano8f62db92007-02-01 00:22:221684
1685-------------------------------------------------
1686$ git fsck
1687dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1688dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1689dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1690...
1691-------------------------------------------------
1692
Junio C Hamano39381a72007-02-02 07:35:151693You can examine
Junio C Hamano8f62db92007-02-01 00:22:221694one of those dangling commits with, for example,
1695
1696------------------------------------------------
1697$ gitk 7281251ddd --not --all
1698------------------------------------------------
1699
1700which does what it sounds like: it says that you want to see the commit
1701history that is described by the dangling commit(s), but not the
1702history that is described by all your existing branches and tags. Thus
1703you get exactly the history reachable from that commit that is lost.
1704(And notice that it might not be just one commit: we only report the
1705"tip of the line" as being dangling, but there might be a whole deep
Junio C Hamanodb911ee2007-02-28 08:13:521706and complex commit history that was dropped.)
Junio C Hamano8f62db92007-02-01 00:22:221707
1708If you decide you want the history back, you can always create a new
1709reference pointing to it, for example, a new branch:
1710
1711------------------------------------------------
Junio C Hamanoa77a5132007-06-08 16:13:441712$ git branch recovered-branch 7281251ddd
Junio C Hamano8f62db92007-02-01 00:22:221713------------------------------------------------
1714
Junio C Hamano3d30fd52007-05-08 00:32:531715Other types of dangling objects (blobs and trees) are also possible, and
1716dangling objects can arise in other situations.
Junio C Hamano8f62db92007-02-01 00:22:221717
Junio C Hamano3d30fd52007-05-08 00:32:531718
1719[[sharing-development]]
Junio C Hamano8f62db92007-02-01 00:22:221720Sharing development with others
1721===============================
1722
Junio C Hamanoec87f522008-12-10 08:35:251723[[getting-updates-With-git-pull]]
Junio C Hamano5f9a6f02009-04-06 08:26:561724Getting updates with git pull
Junio C Hamano8f62db92007-02-01 00:22:221725-----------------------------
1726
Junio C Hamano5706e0b2009-11-24 10:54:161727After you clone a repository and commit a few changes of your own, you
Junio C Hamano8f62db92007-02-01 00:22:221728may wish to check the original repository for updates and merge them
1729into your own work.
1730
Junio C Hamanoec87f522008-12-10 08:35:251731We have already seen <<Updating-a-repository-With-git-fetch,how to
Junio C Hamano97bcb482010-11-25 03:16:071732keep remote-tracking branches up to date>> with linkgit:git-fetch[1],
Junio C Hamano8f62db92007-02-01 00:22:221733and how to merge two branches. So you can merge in changes from the
1734original repository's master branch with:
1735
1736-------------------------------------------------
1737$ git fetch
1738$ git merge origin/master
1739-------------------------------------------------
1740
Junio C Hamano35738e82008-01-07 07:55:461741However, the linkgit:git-pull[1] command provides a way to do this in
Junio C Hamano8f62db92007-02-01 00:22:221742one step:
1743
1744-------------------------------------------------
1745$ git pull origin master
1746-------------------------------------------------
1747
Junio C Hamano947ab822013-03-19 23:07:291748In fact, if you have `master` checked out, then this branch has been
1749configured by `git clone` to get changes from the HEAD branch of the
Junio C Hamano97bcb482010-11-25 03:16:071750origin repository. So often you can
Junio C Hamano4cd1c0e2007-08-06 04:39:141751accomplish the above with just a simple
Junio C Hamano8f62db92007-02-01 00:22:221752
1753-------------------------------------------------
1754$ git pull
1755-------------------------------------------------
1756
Junio C Hamano97bcb482010-11-25 03:16:071757This command will fetch changes from the remote branches to your
1758remote-tracking branches `origin/*`, and merge the default branch into
1759the current branch.
1760
1761More generally, a branch that is created from a remote-tracking branch
1762will pull
Junio C Hamano4cd1c0e2007-08-06 04:39:141763by default from that branch. See the descriptions of the
Junio C Hamano947ab822013-03-19 23:07:291764`branch.<name>.remote` and `branch.<name>.merge` options in
Junio C Hamano35738e82008-01-07 07:55:461765linkgit:git-config[1], and the discussion of the `--track` option in
1766linkgit:git-checkout[1], to learn how to control these defaults.
Junio C Hamano8f62db92007-02-01 00:22:221767
Junio C Hamano947ab822013-03-19 23:07:291768In addition to saving you keystrokes, `git pull` also helps you by
Junio C Hamano8f62db92007-02-01 00:22:221769producing a default commit message documenting the branch and
1770repository that you pulled from.
1771
1772(But note that no such commit will be created in the case of a
Junio C Hamano3f680f32009-11-16 02:10:541773<<fast-forwards,fast-forward>>; instead, your branch will just be
Junio C Hamanodb911ee2007-02-28 08:13:521774updated to point to the latest commit from the upstream branch.)
Junio C Hamano8f62db92007-02-01 00:22:221775
Junio C Hamano947ab822013-03-19 23:07:291776The `git pull` command can also be given `.` as the "remote" repository,
Junio C Hamano8f62db92007-02-01 00:22:221777in which case it just merges in a branch from the current repository; so
1778the commands
1779
1780-------------------------------------------------
1781$ git pull . branch
1782$ git merge branch
1783-------------------------------------------------
1784
Junio C Hamanoe6f28d02013-09-17 21:34:001785are roughly equivalent.
Junio C Hamano8f62db92007-02-01 00:22:221786
Junio C Hamano3d30fd52007-05-08 00:32:531787[[submitting-patches]]
Junio C Hamano8f62db92007-02-01 00:22:221788Submitting patches to a project
1789-------------------------------
1790
1791If you just have a few changes, the simplest way to submit them may
1792just be to send them as patches in email:
1793
Junio C Hamano35738e82008-01-07 07:55:461794First, use linkgit:git-format-patch[1]; for example:
Junio C Hamano8f62db92007-02-01 00:22:221795
1796-------------------------------------------------
1797$ git format-patch origin
1798-------------------------------------------------
1799
1800will produce a numbered series of files in the current directory, one
Junio C Hamano947ab822013-03-19 23:07:291801for each patch in the current branch but not in `origin/HEAD`.
Junio C Hamano8f62db92007-02-01 00:22:221802
Junio C Hamano4eb2b9c2012-11-15 21:12:291803`git format-patch` can include an initial "cover letter". You can insert
1804commentary on individual patches after the three dash line which
1805`format-patch` places after the commit message but before the patch
1806itself. If you use `git notes` to track your cover letter material,
1807`git format-patch --notes` will include the commit's notes in a similar
1808manner.
1809
Junio C Hamano8f62db92007-02-01 00:22:221810You can then import these into your mail client and send them by
1811hand. However, if you have a lot to send at once, you may prefer to
Junio C Hamano35738e82008-01-07 07:55:461812use the linkgit:git-send-email[1] script to automate the process.
Junio C Hamanoc8c398a2014-06-16 21:14:051813Consult the mailing list for your project first to determine
1814their requirements for submitting patches.
Junio C Hamano8f62db92007-02-01 00:22:221815
Junio C Hamano3d30fd52007-05-08 00:32:531816[[importing-patches]]
Junio C Hamano8f62db92007-02-01 00:22:221817Importing patches to a project
1818------------------------------
1819
Junio C Hamano35738e82008-01-07 07:55:461820Git also provides a tool called linkgit:git-am[1] (am stands for
Junio C Hamano8f62db92007-02-01 00:22:221821"apply mailbox"), for importing such an emailed series of patches.
1822Just save all of the patch-containing messages, in order, into a
Junio C Hamano947ab822013-03-19 23:07:291823single mailbox file, say `patches.mbox`, then run
Junio C Hamano8f62db92007-02-01 00:22:221824
1825-------------------------------------------------
1826$ git am -3 patches.mbox
1827-------------------------------------------------
1828
1829Git will apply each patch in order; if any conflicts are found, it
1830will stop, and you can fix the conflicts as described in
Junio C Hamano947ab822013-03-19 23:07:291831"<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells
Junio C Hamano076ffcc2013-02-06 05:13:211832Git to perform a merge; if you would prefer it just to abort and
Junio C Hamano8f62db92007-02-01 00:22:221833leave your tree and index untouched, you may omit that option.)
1834
1835Once the index is updated with the results of the conflict
1836resolution, instead of creating a new commit, just run
1837
1838-------------------------------------------------
Junio C Hamanoa1952302013-07-01 21:31:181839$ git am --continue
Junio C Hamano8f62db92007-02-01 00:22:221840-------------------------------------------------
1841
Junio C Hamano076ffcc2013-02-06 05:13:211842and Git will create the commit for you and continue applying the
Junio C Hamano8f62db92007-02-01 00:22:221843remaining patches from the mailbox.
1844
1845The final result will be a series of commits, one for each patch in
1846the original mailbox, with authorship and commit log message each
1847taken from the message containing each patch.
1848
Junio C Hamano75485c82007-05-19 04:20:331849[[public-repositories]]
Junio C Hamano076ffcc2013-02-06 05:13:211850Public Git repositories
Junio C Hamano75485c82007-05-19 04:20:331851-----------------------
Junio C Hamano8f62db92007-02-01 00:22:221852
Junio C Hamano8b8b0f22007-08-26 22:10:261853Another way to submit changes to a project is to tell the maintainer
1854of that project to pull the changes from your repository using
Junio C Hamanoec87f522008-12-10 08:35:251855linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull,
Junio C Hamano5f9a6f02009-04-06 08:26:561856Getting updates with `git pull`>>" we described this as a way to get
Junio C Hamano8b8b0f22007-08-26 22:10:261857updates from the "main" repository, but it works just as well in the
1858other direction.
Junio C Hamano8f62db92007-02-01 00:22:221859
Junio C Hamano75485c82007-05-19 04:20:331860If you and the maintainer both have accounts on the same machine, then
1861you can just pull changes from each other's repositories directly;
Junio C Hamano2a8f6dc2007-07-09 08:48:381862commands that accept repository URLs as arguments will also accept a
Junio C Hamano75485c82007-05-19 04:20:331863local directory name:
Junio C Hamano8f62db92007-02-01 00:22:221864
1865-------------------------------------------------
1866$ git clone /path/to/repository
1867$ git pull /path/to/other/repository
1868-------------------------------------------------
1869
Junio C Hamano764a6672007-10-23 01:23:311870or an ssh URL:
Junio C Hamano2a8f6dc2007-07-09 08:48:381871
1872-------------------------------------------------
1873$ git clone ssh://yourhost/~you/repository
1874-------------------------------------------------
1875
1876For projects with few developers, or for synchronizing a few private
1877repositories, this may be all you need.
1878
Junio C Hamano75485c82007-05-19 04:20:331879However, the more common way to do this is to maintain a separate public
1880repository (usually on a different host) for others to pull changes
1881from. This is usually more convenient, and allows you to cleanly
1882separate private work in progress from publicly visible work.
Junio C Hamano8f62db92007-02-01 00:22:221883
1884You will continue to do your day-to-day work in your personal
1885repository, but periodically "push" changes from your personal
1886repository into your public repository, allowing other developers to
1887pull from that repository. So the flow of changes, in a situation
1888where there is one other developer with a public repository, looks
1889like this:
1890
1891 you push
1892 your personal repo ------------------> your public repo
Junio C Hamanoa77a5132007-06-08 16:13:441893^ |
Junio C Hamano8f62db92007-02-01 00:22:221894| |
1895| you pull | they pull
1896| |
1897| |
1898 | they push V
1899 their public repo <------------------- their repo
1900
Junio C Hamano2a8f6dc2007-07-09 08:48:381901We explain how to do this in the following sections.
1902
Junio C Hamano75485c82007-05-19 04:20:331903[[setting-up-a-public-repository]]
1904Setting up a public repository
1905~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1906
Junio C Hamano947ab822013-03-19 23:07:291907Assume your personal repository is in the directory `~/proj`. We
Junio C Hamano5f9a6f02009-04-06 08:26:561908first create a new clone of the repository and tell `git daemon` that it
Junio C Hamano75485c82007-05-19 04:20:331909is meant to be public:
Junio C Hamano8f62db92007-02-01 00:22:221910
1911-------------------------------------------------
Junio C Hamano91d44c52007-05-09 07:16:071912$ git clone --bare ~/proj proj.git
Junio C Hamano75485c82007-05-19 04:20:331913$ touch proj.git/git-daemon-export-ok
Junio C Hamano8f62db92007-02-01 00:22:221914-------------------------------------------------
1915
Junio C Hamano91d44c52007-05-09 07:16:071916The resulting directory proj.git contains a "bare" git repository--it is
Junio C Hamano947ab822013-03-19 23:07:291917just the contents of the `.git` directory, without any files checked out
Junio C Hamano75485c82007-05-19 04:20:331918around it.
Junio C Hamano8f62db92007-02-01 00:22:221919
Junio C Hamano947ab822013-03-19 23:07:291920Next, copy `proj.git` to the server where you plan to host the
Junio C Hamano8f62db92007-02-01 00:22:221921public repository. You can use scp, rsync, or whatever is most
1922convenient.
1923
Junio C Hamano75485c82007-05-19 04:20:331924[[exporting-via-git]]
Junio C Hamano076ffcc2013-02-06 05:13:211925Exporting a Git repository via the Git protocol
Junio C Hamano75485c82007-05-19 04:20:331926~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1927
1928This is the preferred method.
1929
1930If someone else administers the server, they should tell you what
Junio C Hamano947ab822013-03-19 23:07:291931directory to put the repository in, and what `git://` URL it will
1932appear at. You can then skip to the section
Junio C Hamano8f62db92007-02-01 00:22:221933"<<pushing-changes-to-a-public-repository,Pushing changes to a public
1934repository>>", below.
1935
Junio C Hamano35738e82008-01-07 07:55:461936Otherwise, all you need to do is start linkgit:git-daemon[1]; it will
Junio C Hamano75485c82007-05-19 04:20:331937listen on port 9418. By default, it will allow access to any directory
Junio C Hamano076ffcc2013-02-06 05:13:211938that looks like a Git directory and contains the magic file
Junio C Hamano5f9a6f02009-04-06 08:26:561939git-daemon-export-ok. Passing some directory paths as `git daemon`
Junio C Hamano75485c82007-05-19 04:20:331940arguments will further restrict the exports to those paths.
1941
Junio C Hamano5f9a6f02009-04-06 08:26:561942You can also run `git daemon` as an inetd service; see the
Junio C Hamano35738e82008-01-07 07:55:461943linkgit:git-daemon[1] man page for details. (See especially the
Junio C Hamano75485c82007-05-19 04:20:331944examples section.)
Junio C Hamano8f62db92007-02-01 00:22:221945
1946[[exporting-via-http]]
Junio C Hamano8c5696d2013-02-11 05:35:001947Exporting a git repository via HTTP
Junio C Hamano75485c82007-05-19 04:20:331948~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:221949
Junio C Hamano076ffcc2013-02-06 05:13:211950The Git protocol gives better performance and reliability, but on a
Junio C Hamano8c5696d2013-02-11 05:35:001951host with a web server set up, HTTP exports may be simpler to set up.
Junio C Hamano8f62db92007-02-01 00:22:221952
Junio C Hamano076ffcc2013-02-06 05:13:211953All you need to do is place the newly created bare Git repository in
Junio C Hamano8f62db92007-02-01 00:22:221954a directory that is exported by the web server, and make some
1955adjustments to give web clients some extra information they need:
1956
1957-------------------------------------------------
1958$ mv proj.git /home/you/public_html/proj.git
1959$ cd proj.git
Junio C Hamano3d30fd52007-05-08 00:32:531960$ git --bare update-server-info
Junio C Hamanoc96fb5a2008-08-12 06:59:381961$ mv hooks/post-update.sample hooks/post-update
Junio C Hamano8f62db92007-02-01 00:22:221962-------------------------------------------------
1963
1964(For an explanation of the last two lines, see
Junio C Hamanofce7c7e2008-07-02 03:06:381965linkgit:git-update-server-info[1] and linkgit:githooks[5].)
Junio C Hamano8f62db92007-02-01 00:22:221966
Junio C Hamano947ab822013-03-19 23:07:291967Advertise the URL of `proj.git`. Anybody else should then be able to
Junio C Hamano764a6672007-10-23 01:23:311968clone or pull from that URL, for example with a command line like:
Junio C Hamano8f62db92007-02-01 00:22:221969
1970-------------------------------------------------
1971$ git clone http://yourserver.com/~you/proj.git
1972-------------------------------------------------
1973
1974(See also
Junio C Hamanoe6f28d02013-09-17 21:34:001975link:howto/setup-git-server-over-http.html[setup-git-server-over-http]
Junio C Hamano8f62db92007-02-01 00:22:221976for a slightly more sophisticated setup using WebDAV which also
Junio C Hamano8c5696d2013-02-11 05:35:001977allows pushing over HTTP.)
Junio C Hamano8f62db92007-02-01 00:22:221978
Junio C Hamano8f62db92007-02-01 00:22:221979[[pushing-changes-to-a-public-repository]]
1980Pushing changes to a public repository
Junio C Hamano75485c82007-05-19 04:20:331981~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:221982
Junio C Hamano75485c82007-05-19 04:20:331983Note that the two techniques outlined above (exporting via
Junio C Hamano8f62db92007-02-01 00:22:221984<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
1985maintainers to fetch your latest changes, but they do not allow write
1986access, which you will need to update the public repository with the
1987latest changes created in your private repository.
1988
Junio C Hamano35738e82008-01-07 07:55:461989The simplest way to do this is using linkgit:git-push[1] and ssh; to
Junio C Hamano947ab822013-03-19 23:07:291990update the remote branch named `master` with the latest state of your
1991branch named `master`, run
Junio C Hamano8f62db92007-02-01 00:22:221992
1993-------------------------------------------------
1994$ git push ssh://yourserver.com/~you/proj.git master:master
1995-------------------------------------------------
1996
1997or just
1998
1999-------------------------------------------------
2000$ git push ssh://yourserver.com/~you/proj.git master
2001-------------------------------------------------
2002
Junio C Hamano5f9a6f02009-04-06 08:26:562003As with `git fetch`, `git push` will complain if this does not result in a
Junio C Hamano3f680f32009-11-16 02:10:542004<<fast-forwards,fast-forward>>; see the following section for details on
Junio C Hamanoce3650e2007-11-26 04:20:112005handling this case.
Junio C Hamano8f62db92007-02-01 00:22:222006
Junio C Hamano947ab822013-03-19 23:07:292007Note that the target of a `push` is normally a
Junio C Hamano2a8f6dc2007-07-09 08:48:382008<<def_bare_repository,bare>> repository. You can also push to a
Junio C Hamano0292db32013-02-15 23:23:282009repository that has a checked-out working tree, but a push to update the
2010currently checked-out branch is denied by default to prevent confusion.
Junio C Hamano5dab5a92013-02-25 18:51:242011See the description of the receive.denyCurrentBranch option
Junio C Hamano0292db32013-02-15 23:23:282012in linkgit:git-config[1] for details.
Junio C Hamano2a8f6dc2007-07-09 08:48:382013
Junio C Hamano5f9a6f02009-04-06 08:26:562014As with `git fetch`, you may also set up configuration options to
Junio C Hamano2da4ac42013-02-19 00:41:172015save typing; so, for example:
Junio C Hamano8f62db92007-02-01 00:22:222016
2017-------------------------------------------------
Junio C Hamano2da4ac42013-02-19 00:41:172018$ git remote add public-repo ssh://yourserver.com/~you/proj.git
2019-------------------------------------------------
2020
2021adds the following to `.git/config`:
2022
2023-------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:222024[remote "public-repo"]
Junio C Hamano2da4ac42013-02-19 00:41:172025url = yourserver.com:proj.git
2026fetch = +refs/heads/*:refs/remotes/example/*
Junio C Hamano8f62db92007-02-01 00:22:222027-------------------------------------------------
2028
Junio C Hamano2da4ac42013-02-19 00:41:172029which lets you do the same push with just
Junio C Hamano8f62db92007-02-01 00:22:222030
2031-------------------------------------------------
2032$ git push public-repo master
2033-------------------------------------------------
2034
Junio C Hamano947ab822013-03-19 23:07:292035See the explanations of the `remote.<name>.url`,
2036`branch.<name>.remote`, and `remote.<name>.push` options in
2037linkgit:git-config[1] for details.
Junio C Hamano8f62db92007-02-01 00:22:222038
Junio C Hamanoce3650e2007-11-26 04:20:112039[[forcing-push]]
2040What to do when a push fails
2041~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2042
Junio C Hamano3f680f32009-11-16 02:10:542043If a push would not result in a <<fast-forwards,fast-forward>> of the
Junio C Hamanoce3650e2007-11-26 04:20:112044remote branch, then it will fail with an error like:
2045
2046-------------------------------------------------
2047error: remote 'refs/heads/master' is not an ancestor of
2048 local 'refs/heads/master'.
2049 Maybe you are not up-to-date and need to pull first?
2050error: failed to push to 'ssh://yourserver.com/~you/proj.git'
2051-------------------------------------------------
2052
2053This can happen, for example, if you:
2054
Junio C Hamano5f9a6f02009-04-06 08:26:562055- use `git reset --hard` to remove already-published commits, or
2056- use `git commit --amend` to replace already-published commits
Junio C Hamanoce3650e2007-11-26 04:20:112057 (as in <<fixing-a-mistake-by-rewriting-history>>), or
Junio C Hamano5f9a6f02009-04-06 08:26:562058- use `git rebase` to rebase any already-published commits (as
Junio C Hamanoce3650e2007-11-26 04:20:112059 in <<using-git-rebase>>).
2060
Junio C Hamano5f9a6f02009-04-06 08:26:562061You may force `git push` to perform the update anyway by preceding the
Junio C Hamanoce3650e2007-11-26 04:20:112062branch name with a plus sign:
2063
2064-------------------------------------------------
2065$ git push ssh://yourserver.com/~you/proj.git +master
2066-------------------------------------------------
2067
Junio C Hamano2da4ac42013-02-19 00:41:172068Note the addition of the `+` sign. Alternatively, you can use the
2069`-f` flag to force the remote update, as in:
2070
2071-------------------------------------------------
2072$ git push -f ssh://yourserver.com/~you/proj.git master
2073-------------------------------------------------
2074
Junio C Hamanoce3650e2007-11-26 04:20:112075Normally whenever a branch head in a public repository is modified, it
Junio C Hamano878cc1e2007-12-14 08:35:132076is modified to point to a descendant of the commit that it pointed to
Junio C Hamanoce3650e2007-11-26 04:20:112077before. By forcing a push in this situation, you break that convention.
Junio C Hamanoec87f522008-12-10 08:35:252078(See <<problems-With-rewriting-history>>.)
Junio C Hamanoce3650e2007-11-26 04:20:112079
2080Nevertheless, this is a common practice for people that need a simple
2081way to publish a work-in-progress patch series, and it is an acceptable
2082compromise as long as you warn other developers that this is how you
2083intend to manage the branch.
2084
2085It's also possible for a push to fail in this way when other people have
2086the right to push to the same repository. In that case, the correct
Junio C Hamanod32738e2008-07-09 19:53:422087solution is to retry the push after first updating your work: either by a
2088pull, or by a fetch followed by a rebase; see the
Junio C Hamanoce3650e2007-11-26 04:20:112089<<setting-up-a-shared-repository,next section>> and
Junio C Hamanofce7c7e2008-07-02 03:06:382090linkgit:gitcvs-migration[7] for more.
Junio C Hamanoce3650e2007-11-26 04:20:112091
Junio C Hamano3d30fd52007-05-08 00:32:532092[[setting-up-a-shared-repository]]
Junio C Hamano8f62db92007-02-01 00:22:222093Setting up a shared repository
Junio C Hamano75485c82007-05-19 04:20:332094~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:222095
2096Another way to collaborate is by using a model similar to that
2097commonly used in CVS, where several developers with special rights
2098all push to and pull from a single shared repository. See
Junio C Hamanofce7c7e2008-07-02 03:06:382099linkgit:gitcvs-migration[7] for instructions on how to
Junio C Hamano8f62db92007-02-01 00:22:222100set this up.
2101
Junio C Hamano076ffcc2013-02-06 05:13:212102However, while there is nothing wrong with Git's support for shared
Junio C Hamanoed7f4f62007-05-20 09:09:092103repositories, this mode of operation is not generally recommended,
Junio C Hamano076ffcc2013-02-06 05:13:212104simply because the mode of collaboration that Git supports--by
Junio C Hamanoed7f4f62007-05-20 09:09:092105exchanging patches and pulling from public repositories--has so many
2106advantages over the central shared repository:
2107
2108- Git's ability to quickly import and merge patches allows a
2109 single maintainer to process incoming changes even at very
Junio C Hamano5f9a6f02009-04-06 08:26:562110 high rates. And when that becomes too much, `git pull` provides
Junio C Hamanoed7f4f62007-05-20 09:09:092111 an easy way for that maintainer to delegate this job to other
2112 maintainers while still allowing optional review of incoming
2113 changes.
2114- Since every developer's repository has the same complete copy
2115 of the project history, no repository is special, and it is
2116 trivial for another developer to take over maintenance of a
2117 project, either by mutual agreement, or because a maintainer
2118 becomes unresponsive or difficult to work with.
2119- The lack of a central group of "committers" means there is
2120 less need for formal decisions about who is "in" and who is
2121 "out".
2122
Junio C Hamano3d30fd52007-05-08 00:32:532123[[setting-up-gitweb]]
Junio C Hamano75485c82007-05-19 04:20:332124Allowing web browsing of a repository
2125~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:222126
2127The gitweb cgi script provides users an easy way to browse your
Junio C Hamano076ffcc2013-02-06 05:13:212128project's files and history without having to install Git; see the file
2129gitweb/INSTALL in the Git source tree for instructions on setting it up.
Junio C Hamano8f62db92007-02-01 00:22:222130
Junio C Hamano3d30fd52007-05-08 00:32:532131[[sharing-development-examples]]
Junio C Hamano8f62db92007-02-01 00:22:222132Examples
2133--------
2134
Junio C Hamano75485c82007-05-19 04:20:332135[[maintaining-topic-branches]]
2136Maintaining topic branches for a Linux subsystem maintainer
2137~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2138
Junio C Hamano076ffcc2013-02-06 05:13:212139This describes how Tony Luck uses Git in his role as maintainer of the
Junio C Hamano75485c82007-05-19 04:20:332140IA64 architecture for the Linux kernel.
2141
2142He uses two public branches:
2143
2144 - A "test" tree into which patches are initially placed so that they
2145 can get some exposure when integrated with other ongoing development.
2146 This tree is available to Andrew for pulling into -mm whenever he
2147 wants.
2148
2149 - A "release" tree into which tested patches are moved for final sanity
2150 checking, and as a vehicle to send them upstream to Linus (by sending
2151 him a "please pull" request.)
2152
2153He also uses a set of temporary branches ("topic branches"), each
2154containing a logical grouping of patches.
2155
2156To set this up, first create your work tree by cloning Linus's public
2157tree:
2158
2159-------------------------------------------------
Junio C Hamanoa1952302013-07-01 21:31:182160$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work
Junio C Hamano75485c82007-05-19 04:20:332161$ cd work
2162-------------------------------------------------
2163
Junio C Hamano97bcb482010-11-25 03:16:072164Linus's tree will be stored in the remote-tracking branch named origin/master,
Junio C Hamano35738e82008-01-07 07:55:462165and can be updated using linkgit:git-fetch[1]; you can track other
2166public trees using linkgit:git-remote[1] to set up a "remote" and
2167linkgit:git-fetch[1] to keep them up-to-date; see
Junio C Hamano8b8b0f22007-08-26 22:10:262168<<repositories-and-branches>>.
Junio C Hamano75485c82007-05-19 04:20:332169
2170Now create the branches in which you are going to work; these start out
2171at the current tip of origin/master branch, and should be set up (using
Junio C Hamano947ab822013-03-19 23:07:292172the `--track` option to linkgit:git-branch[1]) to merge changes in from
Junio C Hamano75485c82007-05-19 04:20:332173Linus by default.
2174
2175-------------------------------------------------
2176$ git branch --track test origin/master
2177$ git branch --track release origin/master
2178-------------------------------------------------
2179
Junio C Hamano35738e82008-01-07 07:55:462180These can be easily kept up to date using linkgit:git-pull[1].
Junio C Hamano75485c82007-05-19 04:20:332181
2182-------------------------------------------------
2183$ git checkout test && git pull
2184$ git checkout release && git pull
2185-------------------------------------------------
2186
2187Important note! If you have any local changes in these branches, then
2188this merge will create a commit object in the history (with no local
Junio C Hamano076ffcc2013-02-06 05:13:212189changes Git will simply do a "fast-forward" merge). Many people dislike
Junio C Hamano75485c82007-05-19 04:20:332190the "noise" that this creates in the Linux history, so you should avoid
Junio C Hamano947ab822013-03-19 23:07:292191doing this capriciously in the `release` branch, as these noisy commits
Junio C Hamano75485c82007-05-19 04:20:332192will become part of the permanent history when you ask Linus to pull
2193from the release branch.
2194
Junio C Hamano35738e82008-01-07 07:55:462195A few configuration variables (see linkgit:git-config[1]) can
Junio C Hamano75485c82007-05-19 04:20:332196make it easy to push both branches to your public tree. (See
2197<<setting-up-a-public-repository>>.)
2198
2199-------------------------------------------------
2200$ cat >> .git/config <<EOF
2201[remote "mytree"]
Junio C Hamanoa1952302013-07-01 21:31:182202url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git
Junio C Hamano75485c82007-05-19 04:20:332203push = release
2204push = test
2205EOF
2206-------------------------------------------------
2207
2208Then you can push both the test and release trees using
Junio C Hamano35738e82008-01-07 07:55:462209linkgit:git-push[1]:
Junio C Hamano75485c82007-05-19 04:20:332210
2211-------------------------------------------------
2212$ git push mytree
2213-------------------------------------------------
2214
2215or push just one of the test and release branches using:
2216
2217-------------------------------------------------
2218$ git push mytree test
2219-------------------------------------------------
2220
2221or
2222
2223-------------------------------------------------
2224$ git push mytree release
2225-------------------------------------------------
2226
2227Now to apply some patches from the community. Think of a short
2228snappy name for a branch to hold this patch (or related group of
Junio C Hamanoc27b7332010-10-14 04:37:282229patches), and create a new branch from a recent stable tag of
2230Linus's branch. Picking a stable base for your branch will:
22311) help you: by avoiding inclusion of unrelated and perhaps lightly
2232tested changes
Junio C Hamano947ab822013-03-19 23:07:2922332) help future bug hunters that use `git bisect` to find problems
Junio C Hamano75485c82007-05-19 04:20:332234
2235-------------------------------------------------
Junio C Hamanoc27b7332010-10-14 04:37:282236$ git checkout -b speed-up-spinlocks v2.6.35
Junio C Hamano75485c82007-05-19 04:20:332237-------------------------------------------------
2238
2239Now you apply the patch(es), run some tests, and commit the change(s). If
2240the patch is a multi-part series, then you should apply each as a separate
2241commit to this branch.
2242
2243-------------------------------------------------
2244$ ... patch ... test ... commit [ ... patch ... test ... commit ]*
2245-------------------------------------------------
2246
Junio C Hamanoe6f28d02013-09-17 21:34:002247When you are happy with the state of this change, you can merge it into the
Junio C Hamano75485c82007-05-19 04:20:332248"test" branch in preparation to make it public:
2249
2250-------------------------------------------------
Junio C Hamanoe6f28d02013-09-17 21:34:002251$ git checkout test && git merge speed-up-spinlocks
Junio C Hamano75485c82007-05-19 04:20:332252-------------------------------------------------
2253
2254It is unlikely that you would have any conflicts here ... but you might if you
2255spent a while on this step and had also pulled new versions from upstream.
2256
Junio C Hamanoc8c398a2014-06-16 21:14:052257Sometime later when enough time has passed and testing done, you can pull the
Junio C Hamano947ab822013-03-19 23:07:292258same branch into the `release` tree ready to go upstream. This is where you
Junio C Hamano75485c82007-05-19 04:20:332259see the value of keeping each patch (or patch series) in its own branch. It
Junio C Hamano947ab822013-03-19 23:07:292260means that the patches can be moved into the `release` tree in any order.
Junio C Hamano75485c82007-05-19 04:20:332261
2262-------------------------------------------------
Junio C Hamanoe6f28d02013-09-17 21:34:002263$ git checkout release && git merge speed-up-spinlocks
Junio C Hamano75485c82007-05-19 04:20:332264-------------------------------------------------
2265
2266After a while, you will have a number of branches, and despite the
2267well chosen names you picked for each of them, you may forget what
2268they are for, or what status they are in. To get a reminder of what
2269changes are in a specific branch, use:
2270
2271-------------------------------------------------
Junio C Hamanoba4b9282008-07-06 05:20:312272$ git log linux..branchname | git shortlog
Junio C Hamano75485c82007-05-19 04:20:332273-------------------------------------------------
2274
Junio C Hamano764a6672007-10-23 01:23:312275To see whether it has already been merged into the test or release branches,
Junio C Hamano75485c82007-05-19 04:20:332276use:
2277
2278-------------------------------------------------
2279$ git log test..branchname
2280-------------------------------------------------
2281
2282or
2283
2284-------------------------------------------------
2285$ git log release..branchname
2286-------------------------------------------------
2287
Junio C Hamano764a6672007-10-23 01:23:312288(If this branch has not yet been merged, you will see some log entries.
Junio C Hamano75485c82007-05-19 04:20:332289If it has been merged, then there will be no output.)
2290
2291Once a patch completes the great cycle (moving from test to release,
2292then pulled by Linus, and finally coming back into your local
Junio C Hamano947ab822013-03-19 23:07:292293`origin/master` branch), the branch for this change is no longer needed.
Junio C Hamano75485c82007-05-19 04:20:332294You detect this when the output from:
2295
2296-------------------------------------------------
2297$ git log origin..branchname
2298-------------------------------------------------
2299
2300is empty. At this point the branch can be deleted:
2301
2302-------------------------------------------------
2303$ git branch -d branchname
2304-------------------------------------------------
2305
2306Some changes are so trivial that it is not necessary to create a separate
2307branch and then merge into each of the test and release branches. For
Junio C Hamano947ab822013-03-19 23:07:292308these changes, just apply directly to the `release` branch, and then
2309merge that into the `test` branch.
Junio C Hamano75485c82007-05-19 04:20:332310
Junio C Hamano5dab5a92013-02-25 18:51:242311After pushing your work to `mytree`, you can use
2312linkgit:git-request-pull[1] to prepare a "please pull" request message
2313to send to Linus:
Junio C Hamano75485c82007-05-19 04:20:332314
2315-------------------------------------------------
Junio C Hamano5dab5a92013-02-25 18:51:242316$ git push mytree
2317$ git request-pull origin mytree release
Junio C Hamano75485c82007-05-19 04:20:332318-------------------------------------------------
2319
2320Here are some of the scripts that simplify all this even further.
2321
2322-------------------------------------------------
2323==== update script ====
Junio C Hamano076ffcc2013-02-06 05:13:212324# Update a branch in my Git tree. If the branch to be updated
Junio C Hamano75485c82007-05-19 04:20:332325# is origin, then pull from kernel.org. Otherwise merge
2326# origin/master branch into test|release branch
2327
2328case "$1" in
2329test|release)
2330git checkout $1 && git pull . origin
2331;;
2332origin)
Junio C Hamano9810d632007-09-24 01:05:342333before=$(git rev-parse refs/remotes/origin/master)
Junio C Hamano75485c82007-05-19 04:20:332334git fetch origin
Junio C Hamano9810d632007-09-24 01:05:342335after=$(git rev-parse refs/remotes/origin/master)
Junio C Hamano75485c82007-05-19 04:20:332336if [ $before != $after ]
2337then
2338git log $before..$after | git shortlog
2339fi
2340;;
2341*)
Junio C Hamano947ab822013-03-19 23:07:292342echo "usage: $0 origin|test|release" 1>&2
Junio C Hamano75485c82007-05-19 04:20:332343exit 1
2344;;
2345esac
2346-------------------------------------------------
2347
2348-------------------------------------------------
2349==== merge script ====
2350# Merge a branch into either the test or release branch
2351
2352pname=$0
2353
2354usage()
2355{
Junio C Hamano947ab822013-03-19 23:07:292356echo "usage: $pname branch test|release" 1>&2
Junio C Hamano75485c82007-05-19 04:20:332357exit 1
2358}
2359
Junio C Hamano9810d632007-09-24 01:05:342360git show-ref -q --verify -- refs/heads/"$1" || {
Junio C Hamano75485c82007-05-19 04:20:332361echo "Can't see branch <$1>" 1>&2
2362usage
Junio C Hamano9810d632007-09-24 01:05:342363}
Junio C Hamano75485c82007-05-19 04:20:332364
2365case "$2" in
2366test|release)
2367if [ $(git log $2..$1 | wc -c) -eq 0 ]
2368then
2369echo $1 already merged into $2 1>&2
2370exit 1
2371fi
2372git checkout $2 && git pull . $1
2373;;
2374*)
2375usage
2376;;
2377esac
2378-------------------------------------------------
2379
2380-------------------------------------------------
2381==== status script ====
Junio C Hamano076ffcc2013-02-06 05:13:212382# report on status of my ia64 Git tree
Junio C Hamano75485c82007-05-19 04:20:332383
2384gb=$(tput setab 2)
2385rb=$(tput setab 1)
2386restore=$(tput setab 9)
2387
2388if [ `git rev-list test..release | wc -c` -gt 0 ]
2389then
2390echo $rb Warning: commits in release that are not in test $restore
2391git log test..release
2392fi
2393
Junio C Hamano9810d632007-09-24 01:05:342394for branch in `git show-ref --heads | sed 's|^.*/||'`
Junio C Hamano75485c82007-05-19 04:20:332395do
2396if [ $branch = test -o $branch = release ]
2397then
2398continue
2399fi
2400
2401echo -n $gb ======= $branch ====== $restore " "
2402status=
2403for ref in test release origin/master
2404do
2405if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
2406then
2407status=$status${ref:0:1}
2408fi
2409done
2410case $status in
2411trl)
2412echo $rb Need to pull into test $restore
2413;;
2414rl)
2415echo "In test"
2416;;
2417l)
2418echo "Waiting for linus"
2419;;
2420"")
2421echo $rb All done $restore
2422;;
2423*)
2424echo $rb "<$status>" $restore
2425;;
2426esac
2427git log origin/master..$branch | git shortlog
2428done
2429-------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:222430
2431
2432[[cleaning-up-history]]
2433Rewriting history and maintaining patch series
2434==============================================
2435
2436Normally commits are only added to a project, never taken away or
2437replaced. Git is designed with this assumption, and violating it will
Junio C Hamano076ffcc2013-02-06 05:13:212438cause Git's merge machinery (for example) to do the wrong thing.
Junio C Hamano8f62db92007-02-01 00:22:222439
2440However, there is a situation in which it can be useful to violate this
2441assumption.
2442
Junio C Hamano3d30fd52007-05-08 00:32:532443[[patch-series]]
Junio C Hamano8f62db92007-02-01 00:22:222444Creating the perfect patch series
2445---------------------------------
2446
2447Suppose you are a contributor to a large project, and you want to add a
2448complicated feature, and to present it to the other developers in a way
2449that makes it easy for them to read your changes, verify that they are
2450correct, and understand why you made each change.
2451
2452If you present all of your changes as a single patch (or commit), they
Junio C Hamanodb911ee2007-02-28 08:13:522453may find that it is too much to digest all at once.
Junio C Hamano8f62db92007-02-01 00:22:222454
2455If you present them with the entire history of your work, complete with
2456mistakes, corrections, and dead ends, they may be overwhelmed.
2457
2458So the ideal is usually to produce a series of patches such that:
2459
24601. Each patch can be applied in order.
2461
24622. Each patch includes a single logical change, together with a
2463 message explaining the change.
2464
24653. No patch introduces a regression: after applying any initial
2466 part of the series, the resulting project still compiles and
2467 works, and has no bugs that it didn't have before.
2468
24694. The complete series produces the same end result as your own
2470 (probably much messier!) development process did.
2471
2472We will introduce some tools that can help you do this, explain how to
2473use them, and then explain some of the problems that can arise because
2474you are rewriting history.
2475
Junio C Hamano3d30fd52007-05-08 00:32:532476[[using-git-rebase]]
Junio C Hamano5f9a6f02009-04-06 08:26:562477Keeping a patch series up to date using git rebase
Junio C Hamano8f62db92007-02-01 00:22:222478--------------------------------------------------
2479
Junio C Hamano947ab822013-03-19 23:07:292480Suppose that you create a branch `mywork` on a remote-tracking branch
2481`origin`, and create some commits on top of it:
Junio C Hamano8f62db92007-02-01 00:22:222482
2483-------------------------------------------------
2484$ git checkout -b mywork origin
2485$ vi file.txt
2486$ git commit
2487$ vi otherfile.txt
2488$ git commit
2489...
2490-------------------------------------------------
2491
2492You have performed no merges into mywork, so it is just a simple linear
Junio C Hamano947ab822013-03-19 23:07:292493sequence of patches on top of `origin`:
Junio C Hamano8f62db92007-02-01 00:22:222494
Junio C Hamanoc51fede2007-03-12 07:29:202495................................................
Junio C Hamano3b4609d2010-09-30 00:04:342496 o--o--O <-- origin
Junio C Hamano8f62db92007-02-01 00:22:222497 \
Junio C Hamano3b4609d2010-09-30 00:04:342498 a--b--c <-- mywork
Junio C Hamanoc51fede2007-03-12 07:29:202499................................................
Junio C Hamano8f62db92007-02-01 00:22:222500
2501Some more interesting work has been done in the upstream project, and
Junio C Hamano947ab822013-03-19 23:07:292502`origin` has advanced:
Junio C Hamano8f62db92007-02-01 00:22:222503
Junio C Hamanoc51fede2007-03-12 07:29:202504................................................
Junio C Hamano8f62db92007-02-01 00:22:222505 o--o--O--o--o--o <-- origin
2506 \
2507 a--b--c <-- mywork
Junio C Hamanoc51fede2007-03-12 07:29:202508................................................
Junio C Hamano8f62db92007-02-01 00:22:222509
Junio C Hamano947ab822013-03-19 23:07:292510At this point, you could use `pull` to merge your changes back in;
Junio C Hamano8f62db92007-02-01 00:22:222511the result would create a new merge commit, like this:
2512
Junio C Hamanoc51fede2007-03-12 07:29:202513................................................
Junio C Hamano8f62db92007-02-01 00:22:222514 o--o--O--o--o--o <-- origin
2515 \ \
2516 a--b--c--m <-- mywork
Junio C Hamanoc51fede2007-03-12 07:29:202517................................................
Junio C Hamanoa77a5132007-06-08 16:13:442518
Junio C Hamano8f62db92007-02-01 00:22:222519However, if you prefer to keep the history in mywork a simple series of
2520commits without any merges, you may instead choose to use
Junio C Hamano35738e82008-01-07 07:55:462521linkgit:git-rebase[1]:
Junio C Hamano8f62db92007-02-01 00:22:222522
2523-------------------------------------------------
2524$ git checkout mywork
2525$ git rebase origin
2526-------------------------------------------------
2527
2528This will remove each of your commits from mywork, temporarily saving
Junio C Hamano947ab822013-03-19 23:07:292529them as patches (in a directory named `.git/rebase-apply`), update mywork to
Junio C Hamano8f62db92007-02-01 00:22:222530point at the latest version of origin, then apply each of the saved
2531patches to the new mywork. The result will look like:
2532
2533
Junio C Hamanoc51fede2007-03-12 07:29:202534................................................
Junio C Hamano8f62db92007-02-01 00:22:222535 o--o--O--o--o--o <-- origin
2536 \
2537 a'--b'--c' <-- mywork
Junio C Hamanoc51fede2007-03-12 07:29:202538................................................
Junio C Hamano8f62db92007-02-01 00:22:222539
2540In the process, it may discover conflicts. In that case it will stop
Junio C Hamano5f9a6f02009-04-06 08:26:562541and allow you to fix the conflicts; after fixing conflicts, use `git add`
Junio C Hamanoba4b9282008-07-06 05:20:312542to update the index with those contents, and then, instead of
Junio C Hamano5f9a6f02009-04-06 08:26:562543running `git commit`, just run
Junio C Hamano8f62db92007-02-01 00:22:222544
2545-------------------------------------------------
2546$ git rebase --continue
2547-------------------------------------------------
2548
Junio C Hamano076ffcc2013-02-06 05:13:212549and Git will continue applying the rest of the patches.
Junio C Hamano8f62db92007-02-01 00:22:222550
Junio C Hamano764a6672007-10-23 01:23:312551At any point you may use the `--abort` option to abort this process and
Junio C Hamano8f62db92007-02-01 00:22:222552return mywork to the state it had before you started the rebase:
2553
2554-------------------------------------------------
2555$ git rebase --abort
2556-------------------------------------------------
2557
Junio C Hamano5dab5a92013-02-25 18:51:242558If you need to reorder or edit a number of commits in a branch, it may
2559be easier to use `git rebase -i`, which allows you to reorder and
2560squash commits, as well as marking them for individual editing during
2561the rebase. See <<interactive-rebase>> for details, and
2562<<reordering-patch-series>> for alternatives.
2563
Junio C Hamanoce3650e2007-11-26 04:20:112564[[rewriting-one-commit]]
2565Rewriting a single commit
Junio C Hamanoaa83a7d2007-03-05 02:37:292566-------------------------
2567
Junio C Hamanoce3650e2007-11-26 04:20:112568We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the
Junio C Hamanoaa83a7d2007-03-05 02:37:292569most recent commit using
2570
2571-------------------------------------------------
2572$ git commit --amend
2573-------------------------------------------------
2574
2575which will replace the old commit by a new commit incorporating your
2576changes, giving you a chance to edit the old commit message first.
Junio C Hamano5dab5a92013-02-25 18:51:242577This is useful for fixing typos in your last commit, or for adjusting
2578the patch contents of a poorly staged commit.
Junio C Hamanoaa83a7d2007-03-05 02:37:292579
Junio C Hamano5dab5a92013-02-25 18:51:242580If you need to amend commits from deeper in your history, you can
2581use <<interactive-rebase,interactive rebase's `edit` instruction>>.
Junio C Hamanoaa83a7d2007-03-05 02:37:292582
Junio C Hamano3d30fd52007-05-08 00:32:532583[[reordering-patch-series]]
Junio C Hamano8f62db92007-02-01 00:22:222584Reordering or selecting from a patch series
2585-------------------------------------------
2586
Junio C Hamano5dab5a92013-02-25 18:51:242587Sometimes you want to edit a commit deeper in your history. One
2588approach is to use `git format-patch` to create a series of patches
2589and then reset the state to before the patches:
Junio C Hamano8f62db92007-02-01 00:22:222590
2591-------------------------------------------------
2592$ git format-patch origin
2593$ git reset --hard origin
2594-------------------------------------------------
2595
Junio C Hamano5dab5a92013-02-25 18:51:242596Then modify, reorder, or eliminate patches as needed before applying
2597them again with linkgit:git-am[1]:
2598
2599-------------------------------------------------
2600$ git am *.patch
2601-------------------------------------------------
2602
2603[[interactive-rebase]]
2604Using interactive rebases
2605-------------------------
2606
2607You can also edit a patch series with an interactive rebase. This is
2608the same as <<reordering-patch-series,reordering a patch series using
2609`format-patch`>>, so use whichever interface you like best.
2610
2611Rebase your current HEAD on the last commit you want to retain as-is.
2612For example, if you want to reorder the last 5 commits, use:
2613
2614-------------------------------------------------
2615$ git rebase -i HEAD~5
2616-------------------------------------------------
2617
2618This will open your editor with a list of steps to be taken to perform
2619your rebase.
2620
2621-------------------------------------------------
2622pick deadbee The oneline of this commit
2623pick fa1afe1 The oneline of the next commit
2624...
2625
2626# Rebase c0ffeee..deadbee onto c0ffeee
2627#
2628# Commands:
2629# p, pick = use commit
2630# r, reword = use commit, but edit the commit message
2631# e, edit = use commit, but stop for amending
2632# s, squash = use commit, but meld into previous commit
2633# f, fixup = like "squash", but discard this commit's log message
2634# x, exec = run command (the rest of the line) using shell
2635#
2636# These lines can be re-ordered; they are executed from top to bottom.
2637#
2638# If you remove a line here THAT COMMIT WILL BE LOST.
2639#
2640# However, if you remove everything, the rebase will be aborted.
2641#
2642# Note that empty commits are commented out
2643-------------------------------------------------
2644
2645As explained in the comments, you can reorder commits, squash them
2646together, edit commit messages, etc. by editing the list. Once you
2647are satisfied, save the list and close your editor, and the rebase
2648will begin.
2649
2650The rebase will stop where `pick` has been replaced with `edit` or
2651when a step in the list fails to mechanically resolve conflicts and
2652needs your help. When you are done editing and/or resolving conflicts
2653you can continue with `git rebase --continue`. If you decide that
2654things are getting too hairy, you can always bail out with `git rebase
2655--abort`. Even after the rebase is complete, you can still recover
2656the original branch by using the <<reflogs,reflog>>.
2657
2658For a more detailed discussion of the procedure and additional tips,
2659see the "INTERACTIVE MODE" section of linkgit:git-rebase[1].
Junio C Hamano8f62db92007-02-01 00:22:222660
Junio C Hamano3d30fd52007-05-08 00:32:532661[[patch-series-tools]]
Junio C Hamano8f62db92007-02-01 00:22:222662Other tools
2663-----------
2664
Junio C Hamanobf984de2009-11-23 06:11:192665There are numerous other tools, such as StGit, which exist for the
Junio C Hamanodb911ee2007-02-28 08:13:522666purpose of maintaining a patch series. These are outside of the scope of
Junio C Hamano8f62db92007-02-01 00:22:222667this manual.
2668
Junio C Hamanoec87f522008-12-10 08:35:252669[[problems-With-rewriting-history]]
Junio C Hamano8f62db92007-02-01 00:22:222670Problems with rewriting history
2671-------------------------------
2672
2673The primary problem with rewriting the history of a branch has to do
2674with merging. Suppose somebody fetches your branch and merges it into
2675their branch, with a result something like this:
2676
Junio C Hamanoc51fede2007-03-12 07:29:202677................................................
Junio C Hamano8f62db92007-02-01 00:22:222678 o--o--O--o--o--o <-- origin
2679 \ \
2680 t--t--t--m <-- their branch:
Junio C Hamanoc51fede2007-03-12 07:29:202681................................................
Junio C Hamano8f62db92007-02-01 00:22:222682
2683Then suppose you modify the last three commits:
2684
Junio C Hamanoc51fede2007-03-12 07:29:202685................................................
Junio C Hamano8f62db92007-02-01 00:22:222686 o--o--o <-- new head of origin
2687/
2688 o--o--O--o--o--o <-- old head of origin
Junio C Hamanoc51fede2007-03-12 07:29:202689................................................
Junio C Hamano8f62db92007-02-01 00:22:222690
2691If we examined all this history together in one repository, it will
2692look like:
2693
Junio C Hamanoc51fede2007-03-12 07:29:202694................................................
Junio C Hamano8f62db92007-02-01 00:22:222695 o--o--o <-- new head of origin
2696/
2697 o--o--O--o--o--o <-- old head of origin
2698 \ \
2699 t--t--t--m <-- their branch:
Junio C Hamanoc51fede2007-03-12 07:29:202700................................................
Junio C Hamano8f62db92007-02-01 00:22:222701
2702Git has no way of knowing that the new head is an updated version of
2703the old head; it treats this situation exactly the same as it would if
2704two developers had independently done the work on the old and new heads
2705in parallel. At this point, if someone attempts to merge the new head
Junio C Hamano076ffcc2013-02-06 05:13:212706in to their branch, Git will attempt to merge together the two (old and
Junio C Hamano8f62db92007-02-01 00:22:222707new) lines of development, instead of trying to replace the old by the
2708new. The results are likely to be unexpected.
2709
2710You may still choose to publish branches whose history is rewritten,
2711and it may be useful for others to be able to fetch those branches in
2712order to examine or test them, but they should not attempt to pull such
2713branches into their own work.
2714
2715For true distributed development that supports proper merging,
2716published branches should never be rewritten.
2717
Junio C Hamano393e57f2007-11-20 04:53:252718[[bisect-merges]]
2719Why bisecting merge commits can be harder than bisecting linear history
2720-----------------------------------------------------------------------
2721
Junio C Hamano35738e82008-01-07 07:55:462722The linkgit:git-bisect[1] command correctly handles history that
Junio C Hamano393e57f2007-11-20 04:53:252723includes merge commits. However, when the commit that it finds is a
2724merge commit, the user may need to work harder than usual to figure out
2725why that commit introduced a problem.
2726
2727Imagine this history:
2728
2729................................................
2730 ---Z---o---X---...---o---A---C---D
2731 \ /
2732 o---o---Y---...---o---B
2733................................................
2734
2735Suppose that on the upper line of development, the meaning of one
2736of the functions that exists at Z is changed at commit X. The
2737commits from Z leading to A change both the function's
2738implementation and all calling sites that exist at Z, as well
2739as new calling sites they add, to be consistent. There is no
2740bug at A.
2741
2742Suppose that in the meantime on the lower line of development somebody
2743adds a new calling site for that function at commit Y. The
2744commits from Z leading to B all assume the old semantics of that
2745function and the callers and the callee are consistent with each
2746other. There is no bug at B, either.
2747
2748Suppose further that the two development lines merge cleanly at C,
2749so no conflict resolution is required.
2750
2751Nevertheless, the code at C is broken, because the callers added
2752on the lower line of development have not been converted to the new
2753semantics introduced on the upper line of development. So if all
2754you know is that D is bad, that Z is good, and that
Junio C Hamano35738e82008-01-07 07:55:462755linkgit:git-bisect[1] identifies C as the culprit, how will you
Junio C Hamano393e57f2007-11-20 04:53:252756figure out that the problem is due to this change in semantics?
2757
Junio C Hamano5f9a6f02009-04-06 08:26:562758When the result of a `git bisect` is a non-merge commit, you should
Junio C Hamano393e57f2007-11-20 04:53:252759normally be able to discover the problem by examining just that commit.
2760Developers can make this easy by breaking their changes into small
2761self-contained commits. That won't help in the case above, however,
2762because the problem isn't obvious from examination of any single
2763commit; instead, a global view of the development is required. To
2764make matters worse, the change in semantics in the problematic
2765function may be just one small part of the changes in the upper
2766line of development.
2767
2768On the other hand, if instead of merging at C you had rebased the
2769history between Z to B on top of A, you would have gotten this
2770linear history:
2771
2772................................................................
2773 ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*
2774................................................................
2775
2776Bisecting between Z and D* would hit a single culprit commit Y*,
2777and understanding why Y* was broken would probably be easier.
2778
Junio C Hamano076ffcc2013-02-06 05:13:212779Partly for this reason, many experienced Git users, even when
Junio C Hamano393e57f2007-11-20 04:53:252780working on an otherwise merge-heavy project, keep the history
2781linear by rebasing against the latest upstream version before
2782publishing.
2783
Junio C Hamano3d30fd52007-05-08 00:32:532784[[advanced-branch-management]]
Junio C Hamano8f62db92007-02-01 00:22:222785Advanced branch management
2786==========================
2787
Junio C Hamano3d30fd52007-05-08 00:32:532788[[fetching-individual-branches]]
Junio C Hamano8f62db92007-02-01 00:22:222789Fetching individual branches
2790----------------------------
2791
Junio C Hamano35738e82008-01-07 07:55:462792Instead of using linkgit:git-remote[1], you can also choose just
Junio C Hamano8f62db92007-02-01 00:22:222793to update one branch at a time, and to store it locally under an
2794arbitrary name:
2795
2796-------------------------------------------------
2797$ git fetch origin todo:my-todo-work
2798-------------------------------------------------
2799
Junio C Hamano947ab822013-03-19 23:07:292800The first argument, `origin`, just tells Git to fetch from the
Junio C Hamano076ffcc2013-02-06 05:13:212801repository you originally cloned from. The second argument tells Git
Junio C Hamano947ab822013-03-19 23:07:292802to fetch the branch named `todo` from the remote repository, and to
2803store it locally under the name `refs/heads/my-todo-work`.
Junio C Hamano8f62db92007-02-01 00:22:222804
2805You can also fetch branches from other repositories; so
2806
2807-------------------------------------------------
2808$ git fetch git://example.com/proj.git master:example-master
2809-------------------------------------------------
2810
Junio C Hamano947ab822013-03-19 23:07:292811will create a new branch named `example-master` and store in it the
2812branch named `master` from the repository at the given URL. If you
Junio C Hamano8f62db92007-02-01 00:22:222813already have a branch named example-master, it will attempt to
Junio C Hamano3d30fd52007-05-08 00:32:532814<<fast-forwards,fast-forward>> to the commit given by example.com's
2815master branch. In more detail:
Junio C Hamano8f62db92007-02-01 00:22:222816
Junio C Hamano3d30fd52007-05-08 00:32:532817[[fetch-fast-forwards]]
2818git fetch and fast-forwards
2819---------------------------
Junio C Hamano8f62db92007-02-01 00:22:222820
Junio C Hamano947ab822013-03-19 23:07:292821In the previous example, when updating an existing branch, `git fetch`
Junio C Hamanoba4b9282008-07-06 05:20:312822checks to make sure that the most recent commit on the remote
Junio C Hamano8f62db92007-02-01 00:22:222823branch is a descendant of the most recent commit on your copy of the
2824branch before updating your copy of the branch to point at the new
Junio C Hamano3f680f32009-11-16 02:10:542825commit. Git calls this process a <<fast-forwards,fast-forward>>.
Junio C Hamano8f62db92007-02-01 00:22:222826
Junio C Hamano3f680f32009-11-16 02:10:542827A fast-forward looks something like this:
Junio C Hamano8f62db92007-02-01 00:22:222828
Junio C Hamanoc51fede2007-03-12 07:29:202829................................................
Junio C Hamano8f62db92007-02-01 00:22:222830 o--o--o--o <-- old head of the branch
2831 \
2832 o--o--o <-- new head of the branch
Junio C Hamanoc51fede2007-03-12 07:29:202833................................................
Junio C Hamano8f62db92007-02-01 00:22:222834
2835
2836In some cases it is possible that the new head will *not* actually be
2837a descendant of the old head. For example, the developer may have
2838realized she made a serious mistake, and decided to backtrack,
2839resulting in a situation like:
2840
Junio C Hamanoc51fede2007-03-12 07:29:202841................................................
Junio C Hamano8f62db92007-02-01 00:22:222842 o--o--o--o--a--b <-- old head of the branch
2843 \
2844 o--o--o <-- new head of the branch
Junio C Hamanoc51fede2007-03-12 07:29:202845................................................
Junio C Hamano8f62db92007-02-01 00:22:222846
Junio C Hamano947ab822013-03-19 23:07:292847In this case, `git fetch` will fail, and print out a warning.
Junio C Hamano8f62db92007-02-01 00:22:222848
Junio C Hamano076ffcc2013-02-06 05:13:212849In that case, you can still force Git to update to the new head, as
Junio C Hamano8f62db92007-02-01 00:22:222850described in the following section. However, note that in the
Junio C Hamano947ab822013-03-19 23:07:292851situation above this may mean losing the commits labeled `a` and `b`,
Junio C Hamano8f62db92007-02-01 00:22:222852unless you've already created a reference of your own pointing to
2853them.
2854
Junio C Hamano3d30fd52007-05-08 00:32:532855[[forcing-fetch]]
Junio C Hamano5f9a6f02009-04-06 08:26:562856Forcing git fetch to do non-fast-forward updates
Junio C Hamano8f62db92007-02-01 00:22:222857------------------------------------------------
2858
2859If git fetch fails because the new head of a branch is not a
2860descendant of the old head, you may force the update with:
2861
2862-------------------------------------------------
2863$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
2864-------------------------------------------------
2865
Junio C Hamano947ab822013-03-19 23:07:292866Note the addition of the `+` sign. Alternatively, you can use the `-f`
Junio C Hamano3d30fd52007-05-08 00:32:532867flag to force updates of all the fetched branches, as in:
Junio C Hamano8f62db92007-02-01 00:22:222868
Junio C Hamano3d30fd52007-05-08 00:32:532869-------------------------------------------------
2870$ git fetch -f origin
2871-------------------------------------------------
2872
2873Be aware that commits that the old version of example/master pointed at
2874may be lost, as we saw in the previous section.
2875
2876[[remote-branch-configuration]]
Junio C Hamano97bcb482010-11-25 03:16:072877Configuring remote-tracking branches
2878------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:222879
Junio C Hamano947ab822013-03-19 23:07:292880We saw above that `origin` is just a shortcut to refer to the
Junio C Hamanodb911ee2007-02-28 08:13:522881repository that you originally cloned from. This information is
Junio C Hamano076ffcc2013-02-06 05:13:212882stored in Git configuration variables, which you can see using
Junio C Hamano35738e82008-01-07 07:55:462883linkgit:git-config[1]:
Junio C Hamano8f62db92007-02-01 00:22:222884
2885-------------------------------------------------
2886$ git config -l
2887core.repositoryformatversion=0
2888core.filemode=true
2889core.logallrefupdates=true
2890remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
2891remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
2892branch.master.remote=origin
2893branch.master.merge=refs/heads/master
2894-------------------------------------------------
2895
2896If there are other repositories that you also use frequently, you can
2897create similar configuration options to save typing; for example,
Junio C Hamano8f62db92007-02-01 00:22:222898
2899-------------------------------------------------
Junio C Hamano2da4ac42013-02-19 00:41:172900$ git remote add example git://example.com/proj.git
Junio C Hamano8f62db92007-02-01 00:22:222901-------------------------------------------------
2902
Junio C Hamano2da4ac42013-02-19 00:41:172903adds the following to `.git/config`:
Junio C Hamano8f62db92007-02-01 00:22:222904
2905-------------------------------------------------
Junio C Hamano2da4ac42013-02-19 00:41:172906[remote "example"]
2907url = git://example.com/proj.git
2908fetch = +refs/heads/*:refs/remotes/example/*
Junio C Hamano8f62db92007-02-01 00:22:222909-------------------------------------------------
2910
Junio C Hamano2da4ac42013-02-19 00:41:172911Also note that the above configuration can be performed by directly
2912editing the file `.git/config` instead of using linkgit:git-remote[1].
2913
2914After configuring the remote, the following three commands will do the
2915same thing:
Junio C Hamano8f62db92007-02-01 00:22:222916
2917-------------------------------------------------
Junio C Hamano2da4ac42013-02-19 00:41:172918$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/*
2919$ git fetch example +refs/heads/*:refs/remotes/example/*
Junio C Hamano8f62db92007-02-01 00:22:222920$ git fetch example
2921-------------------------------------------------
2922
Junio C Hamano35738e82008-01-07 07:55:462923See linkgit:git-config[1] for more details on the configuration
Junio C Hamano2da4ac42013-02-19 00:41:172924options mentioned above and linkgit:git-fetch[1] for more details on
2925the refspec syntax.
Junio C Hamano8f62db92007-02-01 00:22:222926
2927
Junio C Hamano597ffcf2007-09-17 17:33:152928[[git-concepts]]
2929Git concepts
2930============
Junio C Hamano8f62db92007-02-01 00:22:222931
Junio C Hamano597ffcf2007-09-17 17:33:152932Git is built on a small number of simple but powerful ideas. While it
2933is possible to get things done without understanding them, you will find
Junio C Hamano076ffcc2013-02-06 05:13:212934Git much more intuitive if you do.
Junio C Hamano597ffcf2007-09-17 17:33:152935
2936We start with the most important, the <<def_object_database,object
2937database>> and the <<def_index,index>>.
Junio C Hamano8f62db92007-02-01 00:22:222938
Junio C Hamano3d30fd52007-05-08 00:32:532939[[the-object-database]]
Junio C Hamano8f62db92007-02-01 00:22:222940The Object Database
2941-------------------
2942
Junio C Hamano8f62db92007-02-01 00:22:222943
Junio C Hamano597ffcf2007-09-17 17:33:152944We already saw in <<understanding-commits>> that all commits are stored
2945under a 40-digit "object name". In fact, all the information needed to
2946represent the history of a project is stored in objects with such names.
Junio C Hamano5f9a6f02009-04-06 08:26:562947In each case the name is calculated by taking the SHA-1 hash of the
2948contents of the object. The SHA-1 hash is a cryptographic hash function.
Junio C Hamano597ffcf2007-09-17 17:33:152949What that means to us is that it is impossible to find two different
2950objects with the same name. This has a number of advantages; among
2951others:
Junio C Hamano8f62db92007-02-01 00:22:222952
Junio C Hamano597ffcf2007-09-17 17:33:152953- Git can quickly determine whether two objects are identical or not,
2954 just by comparing names.
Junio C Hamano764a6672007-10-23 01:23:312955- Since object names are computed the same way in every repository, the
Junio C Hamano597ffcf2007-09-17 17:33:152956 same content stored in two repositories will always be stored under
2957 the same name.
2958- Git can detect errors when it reads an object, by checking that the
Junio C Hamano5f9a6f02009-04-06 08:26:562959 object's name is still the SHA-1 hash of its contents.
Junio C Hamano8f62db92007-02-01 00:22:222960
Junio C Hamano597ffcf2007-09-17 17:33:152961(See <<object-details>> for the details of the object formatting and
Junio C Hamano5f9a6f02009-04-06 08:26:562962SHA-1 calculation.)
Junio C Hamano8f62db92007-02-01 00:22:222963
Junio C Hamano597ffcf2007-09-17 17:33:152964There are four different types of objects: "blob", "tree", "commit", and
2965"tag".
Junio C Hamano8f62db92007-02-01 00:22:222966
Junio C Hamano597ffcf2007-09-17 17:33:152967- A <<def_blob_object,"blob" object>> is used to store file data.
Junio C Hamanod32738e2008-07-09 19:53:422968- A <<def_tree_object,"tree" object>> ties one or more
Junio C Hamano597ffcf2007-09-17 17:33:152969 "blob" objects into a directory structure. In addition, a tree object
2970 can refer to other tree objects, thus creating a directory hierarchy.
2971- A <<def_commit_object,"commit" object>> ties such directory hierarchies
Junio C Hamano764a6672007-10-23 01:23:312972 together into a <<def_DAG,directed acyclic graph>> of revisions--each
Junio C Hamano597ffcf2007-09-17 17:33:152973 commit contains the object name of exactly one tree designating the
2974 directory hierarchy at the time of the commit. In addition, a commit
2975 refers to "parent" commit objects that describe the history of how we
2976 arrived at that directory hierarchy.
2977- A <<def_tag_object,"tag" object>> symbolically identifies and can be
2978 used to sign other objects. It contains the object name and type of
2979 another object, a symbolic name (of course!) and, optionally, a
2980 signature.
Junio C Hamano8f62db92007-02-01 00:22:222981
2982The object types in some more detail:
2983
Junio C Hamano597ffcf2007-09-17 17:33:152984[[commit-object]]
2985Commit Object
2986~~~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:222987
Junio C Hamano597ffcf2007-09-17 17:33:152988The "commit" object links a physical state of a tree with a description
Junio C Hamano947ab822013-03-19 23:07:292989of how we got there and why. Use the `--pretty=raw` option to
Junio C Hamano35738e82008-01-07 07:55:462990linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite
Junio C Hamano597ffcf2007-09-17 17:33:152991commit:
Junio C Hamano8f62db92007-02-01 00:22:222992
Junio C Hamano597ffcf2007-09-17 17:33:152993------------------------------------------------
2994$ git show -s --pretty=raw 2be7fcb476
2995commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
2996tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
2997parent 257a84d9d02e90447b149af58b271c19405edb6a
2998author Dave Watson <dwatson@mimvista.com> 1187576872 -0400
2999committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700
Junio C Hamano8f62db92007-02-01 00:22:223000
Junio C Hamano597ffcf2007-09-17 17:33:153001 Fix misspelling of 'suppress' in docs
3002
3003 Signed-off-by: Junio C Hamano <gitster@pobox.com>
3004------------------------------------------------
3005
3006As you can see, a commit is defined by:
3007
Junio C Hamano5f9a6f02009-04-06 08:26:563008- a tree: The SHA-1 name of a tree object (as defined below), representing
Junio C Hamano597ffcf2007-09-17 17:33:153009 the contents of a directory at a certain point in time.
Junio C Hamano44dcd492012-07-24 04:35:383010- parent(s): The SHA-1 name(s) of some number of commits which represent the
Junio C Hamano878cc1e2007-12-14 08:35:133011 immediately previous step(s) in the history of the project. The
Junio C Hamano597ffcf2007-09-17 17:33:153012 example above has one parent; merge commits may have more than
3013 one. A commit with no parents is called a "root" commit, and
3014 represents the initial revision of a project. Each project must have
3015 at least one root. A project can also have multiple roots, though
3016 that isn't common (or necessarily a good idea).
3017- an author: The name of the person responsible for this change, together
3018 with its date.
3019- a committer: The name of the person who actually created the commit,
3020 with the date it was done. This may be different from the author, for
3021 example, if the author was someone who wrote a patch and emailed it
3022 to the person who used it to create the commit.
3023- a comment describing this commit.
3024
3025Note that a commit does not itself contain any information about what
3026actually changed; all changes are calculated by comparing the contents
3027of the tree referred to by this commit with the trees associated with
Junio C Hamano076ffcc2013-02-06 05:13:213028its parents. In particular, Git does not attempt to record file renames
Junio C Hamano597ffcf2007-09-17 17:33:153029explicitly, though it can identify cases where the existence of the same
3030file data at changing paths suggests a rename. (See, for example, the
Junio C Hamano947ab822013-03-19 23:07:293031`-M` option to linkgit:git-diff[1]).
Junio C Hamano597ffcf2007-09-17 17:33:153032
Junio C Hamano35738e82008-01-07 07:55:463033A commit is usually created by linkgit:git-commit[1], which creates a
Junio C Hamano597ffcf2007-09-17 17:33:153034commit whose parent is normally the current HEAD, and whose tree is
3035taken from the content currently stored in the index.
Junio C Hamano8f62db92007-02-01 00:22:223036
Junio C Hamano3d30fd52007-05-08 00:32:533037[[tree-object]]
Junio C Hamano8f62db92007-02-01 00:22:223038Tree Object
Junio C Hamano597ffcf2007-09-17 17:33:153039~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:223040
Junio C Hamano35738e82008-01-07 07:55:463041The ever-versatile linkgit:git-show[1] command can also be used to
3042examine tree objects, but linkgit:git-ls-tree[1] will give you more
Junio C Hamano597ffcf2007-09-17 17:33:153043details:
Junio C Hamano8f62db92007-02-01 00:22:223044
Junio C Hamano597ffcf2007-09-17 17:33:153045------------------------------------------------
3046$ git ls-tree fb3a8bdd0ce
3047100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
3048100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
3049100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
3050040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
3051100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
3052100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
3053100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
3054100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
3055...
3056------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:223057
Junio C Hamano597ffcf2007-09-17 17:33:153058As you can see, a tree object contains a list of entries, each with a
Junio C Hamano5f9a6f02009-04-06 08:26:563059mode, object type, SHA-1 name, and name, sorted by name. It represents
Junio C Hamano597ffcf2007-09-17 17:33:153060the contents of a single directory tree.
Junio C Hamano8f62db92007-02-01 00:22:223061
Junio C Hamano597ffcf2007-09-17 17:33:153062The object type may be a blob, representing the contents of a file, or
3063another tree, representing the contents of a subdirectory. Since trees
Junio C Hamano5f9a6f02009-04-06 08:26:563064and blobs, like all other objects, are named by the SHA-1 hash of their
3065contents, two trees have the same SHA-1 name if and only if their
Junio C Hamano597ffcf2007-09-17 17:33:153066contents (including, recursively, the contents of all subdirectories)
Junio C Hamano076ffcc2013-02-06 05:13:213067are identical. This allows Git to quickly determine the differences
Junio C Hamano597ffcf2007-09-17 17:33:153068between two related tree objects, since it can ignore any entries with
3069identical object names.
Junio C Hamano8f62db92007-02-01 00:22:223070
Junio C Hamano597ffcf2007-09-17 17:33:153071(Note: in the presence of submodules, trees may also have commits as
Junio C Hamano4fd58d42007-09-30 00:51:143072entries. See <<submodules>> for documentation.)
Junio C Hamano8f62db92007-02-01 00:22:223073
Junio C Hamano076ffcc2013-02-06 05:13:213074Note that the files all have mode 644 or 755: Git actually only pays
Junio C Hamano597ffcf2007-09-17 17:33:153075attention to the executable bit.
Junio C Hamano8f62db92007-02-01 00:22:223076
Junio C Hamano597ffcf2007-09-17 17:33:153077[[blob-object]]
3078Blob Object
3079~~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:223080
Junio C Hamano35738e82008-01-07 07:55:463081You can use linkgit:git-show[1] to examine the contents of a blob; take,
Junio C Hamano947ab822013-03-19 23:07:293082for example, the blob in the entry for `COPYING` from the tree above:
Junio C Hamano8f62db92007-02-01 00:22:223083
Junio C Hamano597ffcf2007-09-17 17:33:153084------------------------------------------------
3085$ git show 6ff87c4664
Junio C Hamano8f62db92007-02-01 00:22:223086
Junio C Hamano597ffcf2007-09-17 17:33:153087 Note that the only valid version of the GPL as far as this project
3088 is concerned is _this_ particular version of the license (ie v2, not
3089 v2.2 or v3.x or whatever), unless explicitly otherwise stated.
3090...
3091------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:223092
Junio C Hamano597ffcf2007-09-17 17:33:153093A "blob" object is nothing but a binary blob of data. It doesn't refer
3094to anything else or have attributes of any kind.
Junio C Hamano8f62db92007-02-01 00:22:223095
Junio C Hamano597ffcf2007-09-17 17:33:153096Since the blob is entirely defined by its data, if two files in a
3097directory tree (or in multiple different versions of the repository)
3098have the same contents, they will share the same blob object. The object
3099is totally independent of its location in the directory tree, and
3100renaming a file does not change the object that file is associated with.
3101
3102Note that any tree or blob object can be examined using
Junio C Hamano35738e82008-01-07 07:55:463103linkgit:git-show[1] with the <revision>:<path> syntax. This can
Junio C Hamano597ffcf2007-09-17 17:33:153104sometimes be useful for browsing the contents of a tree that is not
3105currently checked out.
Junio C Hamano8f62db92007-02-01 00:22:223106
Junio C Hamano3d30fd52007-05-08 00:32:533107[[trust]]
Junio C Hamano8f62db92007-02-01 00:22:223108Trust
Junio C Hamano597ffcf2007-09-17 17:33:153109~~~~~
Junio C Hamano8f62db92007-02-01 00:22:223110
Junio C Hamano5f9a6f02009-04-06 08:26:563111If you receive the SHA-1 name of a blob from one source, and its contents
Junio C Hamano597ffcf2007-09-17 17:33:153112from another (possibly untrusted) source, you can still trust that those
Junio C Hamano5f9a6f02009-04-06 08:26:563113contents are correct as long as the SHA-1 name agrees. This is because
3114the SHA-1 is designed so that it is infeasible to find different contents
Junio C Hamano597ffcf2007-09-17 17:33:153115that produce the same hash.
Junio C Hamano8f62db92007-02-01 00:22:223116
Junio C Hamano5f9a6f02009-04-06 08:26:563117Similarly, you need only trust the SHA-1 name of a top-level tree object
Junio C Hamano597ffcf2007-09-17 17:33:153118to trust the contents of the entire directory that it refers to, and if
Junio C Hamano5f9a6f02009-04-06 08:26:563119you receive the SHA-1 name of a commit from a trusted source, then you
Junio C Hamano597ffcf2007-09-17 17:33:153120can easily verify the entire history of commits reachable through
3121parents of that commit, and all of those contents of the trees referred
3122to by those commits.
Junio C Hamano8f62db92007-02-01 00:22:223123
3124So to introduce some real trust in the system, the only thing you need
3125to do is to digitally sign just 'one' special note, which includes the
3126name of a top-level commit. Your digital signature shows others
3127that you trust that commit, and the immutability of the history of
3128commits tells others that they can trust the whole history.
3129
3130In other words, you can easily validate a whole archive by just
Junio C Hamano5f9a6f02009-04-06 08:26:563131sending out a single email that tells the people the name (SHA-1 hash)
Junio C Hamano8f62db92007-02-01 00:22:223132of the top commit, and digitally sign that email using something
3133like GPG/PGP.
3134
Junio C Hamano076ffcc2013-02-06 05:13:213135To assist in this, Git also provides the tag object...
Junio C Hamano8f62db92007-02-01 00:22:223136
Junio C Hamano3d30fd52007-05-08 00:32:533137[[tag-object]]
Junio C Hamano8f62db92007-02-01 00:22:223138Tag Object
Junio C Hamano597ffcf2007-09-17 17:33:153139~~~~~~~~~~
Junio C Hamano8f62db92007-02-01 00:22:223140
Junio C Hamano597ffcf2007-09-17 17:33:153141A tag object contains an object, object type, tag name, the name of the
3142person ("tagger") who created the tag, and a message, which may contain
Junio C Hamanod32738e2008-07-09 19:53:423143a signature, as can be seen using linkgit:git-cat-file[1]:
Junio C Hamano8f62db92007-02-01 00:22:223144
Junio C Hamano597ffcf2007-09-17 17:33:153145------------------------------------------------
3146$ git cat-file tag v1.5.0
3147object 437b1b20df4b356c9342dac8d38849f24ef44f27
3148type commit
3149tag v1.5.0
3150tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000
Junio C Hamano8f62db92007-02-01 00:22:223151
Junio C Hamano597ffcf2007-09-17 17:33:153152GIT 1.5.0
3153-----BEGIN PGP SIGNATURE-----
3154Version: GnuPG v1.4.6 (GNU/Linux)
Junio C Hamano8f62db92007-02-01 00:22:223155
Junio C Hamano597ffcf2007-09-17 17:33:153156iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui
3157nLE/L9aUXdWeTFPron96DLA=
3158=2E+0
3159-----END PGP SIGNATURE-----
3160------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:223161
Junio C Hamano35738e82008-01-07 07:55:463162See the linkgit:git-tag[1] command to learn how to create and verify tag
3163objects. (Note that linkgit:git-tag[1] can also be used to create
Junio C Hamano597ffcf2007-09-17 17:33:153164"lightweight tags", which are not tag objects at all, but just simple
Junio C Hamano947ab822013-03-19 23:07:293165references whose names begin with `refs/tags/`).
Junio C Hamano597ffcf2007-09-17 17:33:153166
3167[[pack-files]]
Junio C Hamano076ffcc2013-02-06 05:13:213168How Git stores objects efficiently: pack files
Junio C Hamano597ffcf2007-09-17 17:33:153169~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3170
3171Newly created objects are initially created in a file named after the
Junio C Hamano947ab822013-03-19 23:07:293172object's SHA-1 hash (stored in `.git/objects`).
Junio C Hamano597ffcf2007-09-17 17:33:153173
3174Unfortunately this system becomes inefficient once a project has a
3175lot of objects. Try this on an old project:
3176
3177------------------------------------------------
3178$ git count-objects
31796930 objects, 47620 kilobytes
3180------------------------------------------------
3181
3182The first number is the number of objects which are kept in
3183individual files. The second is the amount of space taken up by
3184those "loose" objects.
3185
Junio C Hamano076ffcc2013-02-06 05:13:213186You can save space and make Git faster by moving these loose objects in
Junio C Hamano597ffcf2007-09-17 17:33:153187to a "pack file", which stores a group of objects in an efficient
3188compressed format; the details of how pack files are formatted can be
Junio C Hamanoe6f28d02013-09-17 21:34:003189found in link:technical/pack-format.html[pack format].
Junio C Hamano597ffcf2007-09-17 17:33:153190
3191To put the loose objects into a pack, just run git repack:
3192
3193------------------------------------------------
3194$ git repack
Junio C Hamanoe6f28d02013-09-17 21:34:003195Counting objects: 6020, done.
3196Delta compression using up to 4 threads.
3197Compressing objects: 100% (6020/6020), done.
3198Writing objects: 100% (6020/6020), done.
3199Total 6020 (delta 4070), reused 0 (delta 0)
Junio C Hamano597ffcf2007-09-17 17:33:153200------------------------------------------------
3201
Junio C Hamanoe6f28d02013-09-17 21:34:003202This creates a single "pack file" in .git/objects/pack/
3203containing all currently unpacked objects. You can then run
Junio C Hamano597ffcf2007-09-17 17:33:153204
3205------------------------------------------------
3206$ git prune
3207------------------------------------------------
3208
3209to remove any of the "loose" objects that are now contained in the
3210pack. This will also remove any unreferenced objects (which may be
Junio C Hamano947ab822013-03-19 23:07:293211created when, for example, you use `git reset` to remove a commit).
Junio C Hamano597ffcf2007-09-17 17:33:153212You can verify that the loose objects are gone by looking at the
Junio C Hamano947ab822013-03-19 23:07:293213`.git/objects` directory or by running
Junio C Hamano597ffcf2007-09-17 17:33:153214
3215------------------------------------------------
3216$ git count-objects
32170 objects, 0 kilobytes
3218------------------------------------------------
3219
3220Although the object files are gone, any commands that refer to those
3221objects will work exactly as they did before.
3222
Junio C Hamano35738e82008-01-07 07:55:463223The linkgit:git-gc[1] command performs packing, pruning, and more for
Junio C Hamano597ffcf2007-09-17 17:33:153224you, so is normally the only high-level command you need.
3225
3226[[dangling-objects]]
3227Dangling objects
3228~~~~~~~~~~~~~~~~
3229
Junio C Hamano35738e82008-01-07 07:55:463230The linkgit:git-fsck[1] command will sometimes complain about dangling
Junio C Hamano597ffcf2007-09-17 17:33:153231objects. They are not a problem.
3232
3233The most common cause of dangling objects is that you've rebased a
3234branch, or you have pulled from somebody else who rebased a branch--see
3235<<cleaning-up-history>>. In that case, the old head of the original
3236branch still exists, as does everything it pointed to. The branch
3237pointer itself just doesn't, since you replaced it with another one.
3238
3239There are also other situations that cause dangling objects. For
Junio C Hamano947ab822013-03-19 23:07:293240example, a "dangling blob" may arise because you did a `git add` of a
Junio C Hamano597ffcf2007-09-17 17:33:153241file, but then, before you actually committed it and made it part of the
3242bigger picture, you changed something else in that file and committed
Junio C Hamano764a6672007-10-23 01:23:313243that *updated* thing--the old state that you added originally ends up
Junio C Hamano597ffcf2007-09-17 17:33:153244not being pointed to by any commit or tree, so it's now a dangling blob
3245object.
3246
3247Similarly, when the "recursive" merge strategy runs, and finds that
3248there are criss-cross merges and thus more than one merge base (which is
3249fairly unusual, but it does happen), it will generate one temporary
3250midway tree (or possibly even more, if you had lots of criss-crossing
3251merges and more than two merge bases) as a temporary internal merge
3252base, and again, those are real objects, but the end result will not end
3253up pointing to them, so they end up "dangling" in your repository.
3254
3255Generally, dangling objects aren't anything to worry about. They can
3256even be very useful: if you screw something up, the dangling objects can
3257be how you recover your old tree (say, you did a rebase, and realized
Junio C Hamano764a6672007-10-23 01:23:313258that you really didn't want to--you can look at what dangling objects
Junio C Hamano597ffcf2007-09-17 17:33:153259you have, and decide to reset your head to some old dangling state).
3260
3261For commits, you can just use:
3262
3263------------------------------------------------
3264$ gitk <dangling-commit-sha-goes-here> --not --all
3265------------------------------------------------
3266
3267This asks for all the history reachable from the given commit but not
3268from any branch, tag, or other reference. If you decide it's something
3269you want, you can always create a new reference to it, e.g.,
3270
3271------------------------------------------------
3272$ git branch recovered-branch <dangling-commit-sha-goes-here>
3273------------------------------------------------
3274
3275For blobs and trees, you can't do the same, but you can still examine
3276them. You can just do
3277
3278------------------------------------------------
3279$ git show <dangling-blob/tree-sha-goes-here>
3280------------------------------------------------
3281
3282to show what the contents of the blob were (or, for a tree, basically
Junio C Hamano947ab822013-03-19 23:07:293283what the `ls` for that directory was), and that may give you some idea
Junio C Hamano597ffcf2007-09-17 17:33:153284of what the operation was that left that dangling object.
3285
3286Usually, dangling blobs and trees aren't very interesting. They're
3287almost always the result of either being a half-way mergebase (the blob
3288will often even have the conflict markers from a merge in it, if you
3289have had conflicting merges that you fixed up by hand), or simply
Junio C Hamano947ab822013-03-19 23:07:293290because you interrupted a `git fetch` with ^C or something like that,
Junio C Hamano597ffcf2007-09-17 17:33:153291leaving _some_ of the new objects in the object database, but just
3292dangling and useless.
3293
3294Anyway, once you are sure that you're not interested in any dangling
3295state, you can just prune all unreachable objects:
3296
3297------------------------------------------------
3298$ git prune
3299------------------------------------------------
3300
Junio C Hamanoe6f28d02013-09-17 21:34:003301and they'll be gone. (You should only run `git prune` on a quiescent
Junio C Hamano764a6672007-10-23 01:23:313302repository--it's kind of like doing a filesystem fsck recovery: you
Junio C Hamano597ffcf2007-09-17 17:33:153303don't want to do that while the filesystem is mounted.
Junio C Hamanoe6f28d02013-09-17 21:34:003304`git prune` is designed not to cause any harm in such cases of concurrent
3305accesses to a repository but you might receive confusing or scary messages.)
Junio C Hamano8f62db92007-02-01 00:22:223306
Junio C Hamanoce3650e2007-11-26 04:20:113307[[recovering-from-repository-corruption]]
3308Recovering from repository corruption
3309~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3310
Junio C Hamano076ffcc2013-02-06 05:13:213311By design, Git treats data trusted to it with caution. However, even in
3312the absence of bugs in Git itself, it is still possible that hardware or
Junio C Hamanoce3650e2007-11-26 04:20:113313operating system errors could corrupt data.
3314
3315The first defense against such problems is backups. You can back up a
Junio C Hamano076ffcc2013-02-06 05:13:213316Git directory using clone, or just using cp, tar, or any other backup
Junio C Hamanoce3650e2007-11-26 04:20:113317mechanism.
3318
3319As a last resort, you can search for the corrupted objects and attempt
3320to replace them by hand. Back up your repository before attempting this
3321in case you corrupt things even more in the process.
3322
3323We'll assume that the problem is a single missing or corrupted blob,
Junio C Hamano878cc1e2007-12-14 08:35:133324which is sometimes a solvable problem. (Recovering missing trees and
Junio C Hamanoce3650e2007-11-26 04:20:113325especially commits is *much* harder).
3326
3327Before starting, verify that there is corruption, and figure out where
Junio C Hamano35738e82008-01-07 07:55:463328it is with linkgit:git-fsck[1]; this may be time-consuming.
Junio C Hamanoce3650e2007-11-26 04:20:113329
3330Assume the output looks like this:
3331
3332------------------------------------------------
Junio C Hamano81d540a2012-03-02 19:52:473333$ git fsck --full --no-dangling
Junio C Hamanoce3650e2007-11-26 04:20:113334broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
3335 to blob 4b9458b3786228369c63936db65827de3cc06200
3336missing blob 4b9458b3786228369c63936db65827de3cc06200
3337------------------------------------------------
3338
Junio C Hamanoce3650e2007-11-26 04:20:113339Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6
3340points to it. If you could find just one copy of that missing blob
3341object, possibly in some other repository, you could move it into
Junio C Hamano947ab822013-03-19 23:07:293342`.git/objects/4b/9458b3...` and be done. Suppose you can't. You can
Junio C Hamano35738e82008-01-07 07:55:463343still examine the tree that pointed to it with linkgit:git-ls-tree[1],
Junio C Hamanoce3650e2007-11-26 04:20:113344which might output something like:
3345
3346------------------------------------------------
3347$ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
3348100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore
3349100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap
3350100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING
3351...
3352100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile
3353...
3354------------------------------------------------
3355
3356So now you know that the missing blob was the data for a file named
Junio C Hamano947ab822013-03-19 23:07:293357`myfile`. And chances are you can also identify the directory--let's
3358say it's in `somedirectory`. If you're lucky the missing copy might be
Junio C Hamanoce3650e2007-11-26 04:20:113359the same as the copy you have checked out in your working tree at
Junio C Hamano947ab822013-03-19 23:07:293360`somedirectory/myfile`; you can test whether that's right with
Junio C Hamano35738e82008-01-07 07:55:463361linkgit:git-hash-object[1]:
Junio C Hamanoce3650e2007-11-26 04:20:113362
3363------------------------------------------------
3364$ git hash-object -w somedirectory/myfile
3365------------------------------------------------
3366
3367which will create and store a blob object with the contents of
Junio C Hamano5f9a6f02009-04-06 08:26:563368somedirectory/myfile, and output the SHA-1 of that object. if you're
Junio C Hamanoce3650e2007-11-26 04:20:113369extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in
3370which case you've guessed right, and the corruption is fixed!
3371
3372Otherwise, you need more information. How do you tell which version of
3373the file has been lost?
3374
3375The easiest way to do this is with:
3376
3377------------------------------------------------
3378$ git log --raw --all --full-history -- somedirectory/myfile
3379------------------------------------------------
3380
3381Because you're asking for raw output, you'll now get something like
3382
3383------------------------------------------------
3384commit abc
3385Author:
3386Date:
3387...
3388:100644 100644 4b9458b... newsha... M somedirectory/myfile
3389
3390
3391commit xyz
3392Author:
3393Date:
3394
3395...
3396:100644 100644 oldsha... 4b9458b... M somedirectory/myfile
3397------------------------------------------------
3398
Junio C Hamano44dcd492012-07-24 04:35:383399This tells you that the immediately following version of the file was
3400"newsha", and that the immediately preceding version was "oldsha".
Junio C Hamanoce3650e2007-11-26 04:20:113401You also know the commit messages that went with the change from oldsha
3402to 4b9458b and with the change from 4b9458b to newsha.
3403
3404If you've been committing small enough changes, you may now have a good
3405shot at reconstructing the contents of the in-between state 4b9458b.
3406
3407If you can do that, you can now recreate the missing object with
3408
3409------------------------------------------------
3410$ git hash-object -w <recreated-file>
3411------------------------------------------------
3412
3413and your repository is good again!
3414
Junio C Hamano947ab822013-03-19 23:07:293415(Btw, you could have ignored the `fsck`, and started with doing a
Junio C Hamanoce3650e2007-11-26 04:20:113416
3417------------------------------------------------
3418$ git log --raw --all
3419------------------------------------------------
3420
3421and just looked for the sha of the missing object (4b9458b..) in that
Junio C Hamano8c5696d2013-02-11 05:35:003422whole thing. It's up to you--Git does *have* a lot of information, it is
Junio C Hamanoce3650e2007-11-26 04:20:113423just missing one particular blob version.
3424
Junio C Hamano3d30fd52007-05-08 00:32:533425[[the-index]]
Junio C Hamano597ffcf2007-09-17 17:33:153426The index
3427-----------
Junio C Hamano8f62db92007-02-01 00:22:223428
Junio C Hamano947ab822013-03-19 23:07:293429The index is a binary file (generally kept in `.git/index`) containing a
Junio C Hamano5f9a6f02009-04-06 08:26:563430sorted list of path names, each with permissions and the SHA-1 of a blob
Junio C Hamano35738e82008-01-07 07:55:463431object; linkgit:git-ls-files[1] can show you the contents of the index:
Junio C Hamano8f62db92007-02-01 00:22:223432
Junio C Hamano597ffcf2007-09-17 17:33:153433-------------------------------------------------
3434$ git ls-files --stage
3435100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore
3436100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap
3437100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING
3438100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore
3439100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile
3440...
3441100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h
3442100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c
3443100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h
3444-------------------------------------------------
Junio C Hamano8f62db92007-02-01 00:22:223445
Junio C Hamano597ffcf2007-09-17 17:33:153446Note that in older documentation you may see the index called the
3447"current directory cache" or just the "cache". It has three important
3448properties:
Junio C Hamano8f62db92007-02-01 00:22:223449
Junio C Hamano597ffcf2007-09-17 17:33:1534501. The index contains all the information necessary to generate a single
3451(uniquely determined) tree object.
3452+
Junio C Hamano35738e82008-01-07 07:55:463453For example, running linkgit:git-commit[1] generates this tree object
Junio C Hamano597ffcf2007-09-17 17:33:153454from the index, stores it in the object database, and uses it as the
3455tree object associated with the new commit.
Junio C Hamano8f62db92007-02-01 00:22:223456
Junio C Hamano597ffcf2007-09-17 17:33:1534572. The index enables fast comparisons between the tree object it defines
3458and the working tree.
3459+
3460It does this by storing some additional data for each entry (such as
3461the last modified time). This data is not displayed above, and is not
3462stored in the created tree object, but it can be used to determine
3463quickly which files in the working directory differ from what was
Junio C Hamano076ffcc2013-02-06 05:13:213464stored in the index, and thus save Git from having to read all of the
Junio C Hamano597ffcf2007-09-17 17:33:153465data from such files to look for changes.
Junio C Hamano8f62db92007-02-01 00:22:223466
Junio C Hamano597ffcf2007-09-17 17:33:1534673. It can efficiently represent information about merge conflicts
3468between different tree objects, allowing each pathname to be
Junio C Hamano8f62db92007-02-01 00:22:223469associated with sufficient information about the trees involved that
Junio C Hamano597ffcf2007-09-17 17:33:153470you can create a three-way merge between them.
3471+
3472We saw in <<conflict-resolution>> that during a merge the index can
3473store multiple versions of a single file (called "stages"). The third
Junio C Hamano35738e82008-01-07 07:55:463474column in the linkgit:git-ls-files[1] output above is the stage
Junio C Hamano597ffcf2007-09-17 17:33:153475number, and will take on values other than 0 for files with merge
3476conflicts.
Junio C Hamano8f62db92007-02-01 00:22:223477
Junio C Hamano597ffcf2007-09-17 17:33:153478The index is thus a sort of temporary staging area, which is filled with
3479a tree which you are in the process of working on.
Junio C Hamano8f62db92007-02-01 00:22:223480
Junio C Hamano597ffcf2007-09-17 17:33:153481If you blow the index away entirely, you generally haven't lost any
3482information as long as you have the name of the tree that it described.
Junio C Hamano8f62db92007-02-01 00:22:223483
Junio C Hamano9810d632007-09-24 01:05:343484[[submodules]]
3485Submodules
3486==========
3487
Junio C Hamano4fd58d42007-09-30 00:51:143488Large projects are often composed of smaller, self-contained modules. For
3489example, an embedded Linux distribution's source tree would include every
3490piece of software in the distribution with some local modifications; a movie
3491player might need to build against a specific, known-working version of a
3492decompression library; several independent programs might all share the same
3493build scripts.
Junio C Hamano9810d632007-09-24 01:05:343494
Junio C Hamano4fd58d42007-09-30 00:51:143495With centralized revision control systems this is often accomplished by
3496including every module in one single repository. Developers can check out
3497all modules or only the modules they need to work with. They can even modify
3498files across several modules in a single commit while moving things around
3499or updating APIs and translations.
3500
3501Git does not allow partial checkouts, so duplicating this approach in Git
3502would force developers to keep a local copy of modules they are not
3503interested in touching. Commits in an enormous checkout would be slower
3504than you'd expect as Git would have to scan every directory for changes.
3505If modules have a lot of local history, clones would take forever.
3506
3507On the plus side, distributed revision control systems can much better
3508integrate with external sources. In a centralized model, a single arbitrary
3509snapshot of the external project is exported from its own revision control
3510and then imported into the local revision control on a vendor branch. All
3511the history is hidden. With distributed revision control you can clone the
3512entire external history and much more easily follow development and re-merge
3513local changes.
3514
3515Git's submodule support allows a repository to contain, as a subdirectory, a
3516checkout of an external project. Submodules maintain their own identity;
3517the submodule support just stores the submodule repository location and
3518commit ID, so other developers who clone the containing project
3519("superproject") can easily clone all the submodules at the same revision.
3520Partial checkouts of the superproject are possible: you can tell Git to
3521clone none, some or all of the submodules.
3522
Junio C Hamano35738e82008-01-07 07:55:463523The linkgit:git-submodule[1] command is available since Git 1.5.3. Users
Junio C Hamano4fd58d42007-09-30 00:51:143524with Git 1.5.2 can look up the submodule commits in the repository and
3525manually check them out; earlier versions won't recognize the submodules at
3526all.
Junio C Hamano9810d632007-09-24 01:05:343527
Junio C Hamanoe6f28d02013-09-17 21:34:003528To see how submodule support works, create four example
Junio C Hamano9810d632007-09-24 01:05:343529repositories that can be used later as a submodule:
3530
3531-------------------------------------------------
3532$ mkdir ~/git
3533$ cd ~/git
3534$ for i in a b c d
3535do
3536mkdir $i
3537cd $i
3538git init
3539echo "module $i" > $i.txt
3540git add $i.txt
3541git commit -m "Initial commit, submodule $i"
3542cd ..
3543done
3544-------------------------------------------------
3545
3546Now create the superproject and add all the submodules:
3547
3548-------------------------------------------------
3549$ mkdir super
3550$ cd super
3551$ git init
3552$ for i in a b c d
3553do
Junio C Hamano7f80ae82008-07-30 18:31:353554git submodule add ~/git/$i $i
Junio C Hamano9810d632007-09-24 01:05:343555done
3556-------------------------------------------------
3557
3558NOTE: Do not use local URLs here if you plan to publish your superproject!
3559
Junio C Hamano5f9a6f02009-04-06 08:26:563560See what files `git submodule` created:
Junio C Hamano9810d632007-09-24 01:05:343561
3562-------------------------------------------------
3563$ ls -a
3564. .. .git .gitmodules a b c d
3565-------------------------------------------------
3566
Junio C Hamano5f9a6f02009-04-06 08:26:563567The `git submodule add <repo> <path>` command does a couple of things:
Junio C Hamano9810d632007-09-24 01:05:343568
Junio C Hamano947ab822013-03-19 23:07:293569- It clones the submodule from `<repo>` to the given `<path>` under the
Junio C Hamano7f80ae82008-07-30 18:31:353570 current directory and by default checks out the master branch.
Junio C Hamano35738e82008-01-07 07:55:463571- It adds the submodule's clone path to the linkgit:gitmodules[5] file and
Junio C Hamano4fd58d42007-09-30 00:51:143572 adds this file to the index, ready to be committed.
Junio C Hamano9810d632007-09-24 01:05:343573- It adds the submodule's current commit ID to the index, ready to be
3574 committed.
3575
3576Commit the superproject:
3577
3578-------------------------------------------------
3579$ git commit -m "Add submodules a, b, c and d."
3580-------------------------------------------------
3581
3582Now clone the superproject:
3583
3584-------------------------------------------------
3585$ cd ..
3586$ git clone super cloned
3587$ cd cloned
3588-------------------------------------------------
3589
3590The submodule directories are there, but they're empty:
3591
3592-------------------------------------------------
3593$ ls -a a
3594. ..
3595$ git submodule status
3596-d266b9873ad50488163457f025db7cdd9683d88b a
3597-e81d457da15309b4fef4249aba9b50187999670d b
3598-c1536a972b9affea0f16e0680ba87332dc059146 c
3599-d96249ff5d57de5de093e6baff9e0aafa5276a74 d
3600-------------------------------------------------
3601
3602NOTE: The commit object names shown above would be different for you, but they
3603should match the HEAD commit object names of your repositories. You can check
3604it by running `git ls-remote ../a`.
3605
3606Pulling down the submodules is a two-step process. First run `git submodule
3607init` to add the submodule repository URLs to `.git/config`:
3608
3609-------------------------------------------------
3610$ git submodule init
3611-------------------------------------------------
3612
Junio C Hamano5f9a6f02009-04-06 08:26:563613Now use `git submodule update` to clone the repositories and check out the
Junio C Hamano9810d632007-09-24 01:05:343614commits specified in the superproject:
3615
3616-------------------------------------------------
3617$ git submodule update
3618$ cd a
3619$ ls -a
3620. .. .git a.txt
3621-------------------------------------------------
3622
Junio C Hamano5f9a6f02009-04-06 08:26:563623One major difference between `git submodule update` and `git submodule add` is
3624that `git submodule update` checks out a specific commit, rather than the tip
Junio C Hamano9810d632007-09-24 01:05:343625of a branch. It's like checking out a tag: the head is detached, so you're not
3626working on a branch.
3627
3628-------------------------------------------------
3629$ git branch
Junio C Hamanoe6f28d02013-09-17 21:34:003630* (detached from d266b98)
Junio C Hamano9810d632007-09-24 01:05:343631 master
3632-------------------------------------------------
3633
3634If you want to make a change within a submodule and you have a detached head,
3635then you should create or checkout a branch, make your changes, publish the
3636change within the submodule, and then update the superproject to reference the
3637new commit:
3638
3639-------------------------------------------------
3640$ git checkout master
3641-------------------------------------------------
3642
3643or
3644
3645-------------------------------------------------
3646$ git checkout -b fix-up
3647-------------------------------------------------
3648
3649then
3650
3651-------------------------------------------------
3652$ echo "adding a line again" >> a.txt
3653$ git commit -a -m "Updated the submodule from within the superproject."
3654$ git push
3655$ cd ..
3656$ git diff
3657diff --git a/a b/a
3658index d266b98..261dfac 160000
3659--- a/a
3660+++ b/a
3661@@ -1 +1 @@
3662-Subproject commit d266b9873ad50488163457f025db7cdd9683d88b
3663+Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24
3664$ git add a
3665$ git commit -m "Updated submodule a."
3666$ git push
3667-------------------------------------------------
3668
3669You have to run `git submodule update` after `git pull` if you want to update
3670submodules, too.
3671
3672Pitfalls with submodules
3673------------------------
3674
3675Always publish the submodule change before publishing the change to the
3676superproject that references it. If you forget to publish the submodule change,
3677others won't be able to clone the repository:
3678
3679-------------------------------------------------
3680$ cd ~/git/super/a
3681$ echo i added another line to this file >> a.txt
3682$ git commit -a -m "doing it wrong this time"
3683$ cd ..
3684$ git add a
3685$ git commit -m "Updated submodule a again."
3686$ git push
3687$ cd ~/git/cloned
3688$ git pull
3689$ git submodule update
3690error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git.
3691Did you forget to 'git add'?
3692Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a'
3693-------------------------------------------------
3694
Junio C Hamano076ffcc2013-02-06 05:13:213695In older Git versions it could be easily forgotten to commit new or modified
Junio C Hamano2b186d82010-02-02 07:17:343696files in a submodule, which silently leads to similar problems as not pushing
Junio C Hamano947ab822013-03-19 23:07:293697the submodule changes. Starting with Git 1.7.0 both `git status` and `git diff`
Junio C Hamano2b186d82010-02-02 07:17:343698in the superproject show submodules as modified when they contain new or
Junio C Hamano947ab822013-03-19 23:07:293699modified files to protect against accidentally committing such a state. `git
3700diff` will also add a `-dirty` to the work tree side when generating patch
3701output or used with the `--submodule` option:
Junio C Hamano2b186d82010-02-02 07:17:343702
3703-------------------------------------------------
3704$ git diff
3705diff --git a/sub b/sub
3706--- a/sub
3707+++ b/sub
3708@@ -1 +1 @@
3709-Subproject commit 3f356705649b5d566d97ff843cf193359229a453
3710+Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty
3711$ git diff --submodule
3712Submodule sub 3f35670..3f35670-dirty:
3713-------------------------------------------------
3714
Junio C Hamano9810d632007-09-24 01:05:343715You also should not rewind branches in a submodule beyond commits that were
3716ever recorded in any superproject.
3717
3718It's not safe to run `git submodule update` if you've made and committed
3719changes within a submodule without checking out a branch first. They will be
3720silently overwritten:
3721
3722-------------------------------------------------
3723$ cat a.txt
3724module a
3725$ echo line added from private2 >> a.txt
3726$ git commit -a -m "line added inside private2"
3727$ cd ..
3728$ git submodule update
3729Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b'
3730$ cd a
3731$ cat a.txt
3732module a
3733-------------------------------------------------
3734
3735NOTE: The changes are still visible in the submodule's reflog.
3736
Junio C Hamano5dab5a92013-02-25 18:51:243737If you have uncommitted changes in your submodule working tree, `git
3738submodule update` will not overwrite them. Instead, you get the usual
3739warning about not being able switch from a dirty branch.
Junio C Hamano9810d632007-09-24 01:05:343740
Junio C Hamano597ffcf2007-09-17 17:33:153741[[low-level-operations]]
Junio C Hamano076ffcc2013-02-06 05:13:213742Low-level Git operations
Junio C Hamano597ffcf2007-09-17 17:33:153743========================
Junio C Hamano8f62db92007-02-01 00:22:223744
Junio C Hamano597ffcf2007-09-17 17:33:153745Many of the higher-level commands were originally implemented as shell
Junio C Hamano076ffcc2013-02-06 05:13:213746scripts using a smaller core of low-level Git commands. These can still
3747be useful when doing unusual things with Git, or just as a way to
Junio C Hamano597ffcf2007-09-17 17:33:153748understand its inner workings.
3749
3750[[object-manipulation]]
3751Object access and manipulation
3752------------------------------
3753
Junio C Hamano35738e82008-01-07 07:55:463754The linkgit:git-cat-file[1] command can show the contents of any object,
3755though the higher-level linkgit:git-show[1] is usually more useful.
Junio C Hamano597ffcf2007-09-17 17:33:153756
Junio C Hamano35738e82008-01-07 07:55:463757The linkgit:git-commit-tree[1] command allows constructing commits with
Junio C Hamano597ffcf2007-09-17 17:33:153758arbitrary parents and trees.
3759
Junio C Hamano35738e82008-01-07 07:55:463760A tree can be created with linkgit:git-write-tree[1] and its data can be
3761accessed by linkgit:git-ls-tree[1]. Two trees can be compared with
3762linkgit:git-diff-tree[1].
Junio C Hamano597ffcf2007-09-17 17:33:153763
Junio C Hamano35738e82008-01-07 07:55:463764A tag is created with linkgit:git-mktag[1], and the signature can be
3765verified by linkgit:git-verify-tag[1], though it is normally simpler to
3766use linkgit:git-tag[1] for both.
Junio C Hamano8f62db92007-02-01 00:22:223767
Junio C Hamano3d30fd52007-05-08 00:32:533768[[the-workflow]]
Junio C Hamano8f62db92007-02-01 00:22:223769The Workflow
3770------------
3771
Junio C Hamano35738e82008-01-07 07:55:463772High-level operations such as linkgit:git-commit[1],
3773linkgit:git-checkout[1] and linkgit:git-reset[1] work by moving data
Junio C Hamano764a6672007-10-23 01:23:313774between the working tree, the index, and the object database. Git
3775provides low-level operations which perform each of these steps
3776individually.
Junio C Hamano597ffcf2007-09-17 17:33:153777
Junio C Hamano076ffcc2013-02-06 05:13:213778Generally, all Git operations work on the index file. Some operations
Junio C Hamano8f62db92007-02-01 00:22:223779work *purely* on the index file (showing the current state of the
Junio C Hamano597ffcf2007-09-17 17:33:153780index), but most operations move data between the index file and either
3781the database or the working directory. Thus there are four main
3782combinations:
Junio C Hamano8f62db92007-02-01 00:22:223783
Junio C Hamano3d30fd52007-05-08 00:32:533784[[working-directory-to-index]]
Junio C Hamano8f62db92007-02-01 00:22:223785working directory -> index
3786~~~~~~~~~~~~~~~~~~~~~~~~~~
3787
Junio C Hamano35738e82008-01-07 07:55:463788The linkgit:git-update-index[1] command updates the index with
Junio C Hamano597ffcf2007-09-17 17:33:153789information from the working directory. You generally update the
3790index information by just specifying the filename you want to update,
3791like so:
Junio C Hamano8f62db92007-02-01 00:22:223792
3793-------------------------------------------------
Junio C Hamano597ffcf2007-09-17 17:33:153794$ git update-index filename
Junio C Hamano8f62db92007-02-01 00:22:223795-------------------------------------------------
3796
Junio C Hamano826f5c42014-02-07 20:33:303797but to avoid common mistakes with filename globbing etc., the command
Junio C Hamano8f62db92007-02-01 00:22:223798will not normally add totally new entries or remove old entries,
3799i.e. it will normally just update existing cache entries.
3800
Junio C Hamano076ffcc2013-02-06 05:13:213801To tell Git that yes, you really do realize that certain files no
Junio C Hamano8f62db92007-02-01 00:22:223802longer exist, or that new files should be added, you
3803should use the `--remove` and `--add` flags respectively.
3804
3805NOTE! A `--remove` flag does 'not' mean that subsequent filenames will
3806necessarily be removed: if the files still exist in your directory
3807structure, the index will be updated with their new status, not
Junio C Hamano774239c2007-12-01 01:57:433808removed. The only thing `--remove` means is that update-index will be
Junio C Hamano8f62db92007-02-01 00:22:223809considering a removed file to be a valid thing, and if the file really
3810does not exist any more, it will update the index accordingly.
3811
Junio C Hamanoba4b9282008-07-06 05:20:313812As a special case, you can also do `git update-index --refresh`, which
Junio C Hamano8f62db92007-02-01 00:22:223813will refresh the "stat" information of each index to match the current
3814stat information. It will 'not' update the object status itself, and
3815it will only update the fields that are used to quickly test whether
3816an object still matches its old backing store object.
3817
Junio C Hamano35738e82008-01-07 07:55:463818The previously introduced linkgit:git-add[1] is just a wrapper for
3819linkgit:git-update-index[1].
Junio C Hamano597ffcf2007-09-17 17:33:153820
Junio C Hamano3d30fd52007-05-08 00:32:533821[[index-to-object-database]]
Junio C Hamano8f62db92007-02-01 00:22:223822index -> object database
3823~~~~~~~~~~~~~~~~~~~~~~~~
3824
3825You write your current index file to a "tree" object with the program
3826
3827-------------------------------------------------
Junio C Hamano597ffcf2007-09-17 17:33:153828$ git write-tree
Junio C Hamano8f62db92007-02-01 00:22:223829-------------------------------------------------
3830
Junio C Hamano764a6672007-10-23 01:23:313831that doesn't come with any options--it will just write out the
Junio C Hamano8f62db92007-02-01 00:22:223832current index into the set of tree objects that describe that state,
3833and it will return the name of the resulting top-level tree. You can
3834use that tree to re-generate the index at any time by going in the
3835other direction:
3836
Junio C Hamano3d30fd52007-05-08 00:32:533837[[object-database-to-index]]
Junio C Hamano8f62db92007-02-01 00:22:223838object database -> index
3839~~~~~~~~~~~~~~~~~~~~~~~~
3840
3841You read a "tree" file from the object database, and use that to
Junio C Hamano764a6672007-10-23 01:23:313842populate (and overwrite--don't do this if your index contains any
Junio C Hamano8f62db92007-02-01 00:22:223843unsaved state that you might want to restore later!) your current
3844index. Normal operation is just
3845
3846-------------------------------------------------
Junio C Hamano5f9a6f02009-04-06 08:26:563847$ git read-tree <SHA-1 of tree>
Junio C Hamano8f62db92007-02-01 00:22:223848-------------------------------------------------
3849
3850and your index file will now be equivalent to the tree that you saved
3851earlier. However, that is only your 'index' file: your working
3852directory contents have not been modified.
3853
Junio C Hamano3d30fd52007-05-08 00:32:533854[[index-to-working-directory]]
Junio C Hamano8f62db92007-02-01 00:22:223855index -> working directory
3856~~~~~~~~~~~~~~~~~~~~~~~~~~
3857
3858You update your working directory from the index by "checking out"
3859files. This is not a very common operation, since normally you'd just
3860keep your files updated, and rather than write to your working
3861directory, you'd tell the index files about the changes in your
Junio C Hamano5f9a6f02009-04-06 08:26:563862working directory (i.e. `git update-index`).
Junio C Hamano8f62db92007-02-01 00:22:223863
3864However, if you decide to jump to a new version, or check out somebody
3865else's version, or just restore a previous tree, you'd populate your
3866index file with read-tree, and then you need to check out the result
3867with
3868
3869-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:383870$ git checkout-index filename
Junio C Hamano8f62db92007-02-01 00:22:223871-------------------------------------------------
3872
3873or, if you want to check out all of the index, use `-a`.
3874
Junio C Hamano5f9a6f02009-04-06 08:26:563875NOTE! `git checkout-index` normally refuses to overwrite old files, so
Junio C Hamano8f62db92007-02-01 00:22:223876if you have an old version of the tree already checked out, you will
Junio C Hamano947ab822013-03-19 23:07:293877need to use the `-f` flag ('before' the `-a` flag or the filename) to
Junio C Hamano8f62db92007-02-01 00:22:223878'force' the checkout.
3879
3880
3881Finally, there are a few odds and ends which are not purely moving
3882from one representation to the other:
3883
Junio C Hamano3d30fd52007-05-08 00:32:533884[[tying-it-all-together]]
Junio C Hamano8f62db92007-02-01 00:22:223885Tying it all together
3886~~~~~~~~~~~~~~~~~~~~~
3887
Junio C Hamano947ab822013-03-19 23:07:293888To commit a tree you have instantiated with `git write-tree`, you'd
Junio C Hamano8f62db92007-02-01 00:22:223889create a "commit" object that refers to that tree and the history
Junio C Hamano764a6672007-10-23 01:23:313890behind it--most notably the "parent" commits that preceded it in
Junio C Hamano8f62db92007-02-01 00:22:223891history.
3892
3893Normally a "commit" has one parent: the previous state of the tree
3894before a certain change was made. However, sometimes it can have two
3895or more parent commits, in which case we call it a "merge", due to the
3896fact that such a commit brings together ("merges") two or more
3897previous states represented by other commits.
3898
3899In other words, while a "tree" represents a particular directory state
Junio C Hamanoe6f28d02013-09-17 21:34:003900of a working directory, a "commit" represents that state in time,
Junio C Hamano8f62db92007-02-01 00:22:223901and explains how we got there.
3902
3903You create a commit object by giving it the tree that describes the
3904state at the time of the commit, and a list of parents:
3905
3906-------------------------------------------------
Junio C Hamanod2179ef2010-10-22 04:12:173907$ git commit-tree <tree> -p <parent> [(-p <parent2>)...]
Junio C Hamano8f62db92007-02-01 00:22:223908-------------------------------------------------
3909
3910and then giving the reason for the commit on stdin (either through
3911redirection from a pipe or file, or by just typing it at the tty).
3912
Junio C Hamano5f9a6f02009-04-06 08:26:563913`git commit-tree` will return the name of the object that represents
Junio C Hamano8f62db92007-02-01 00:22:223914that commit, and you should save it away for later use. Normally,
Junio C Hamano076ffcc2013-02-06 05:13:213915you'd commit a new `HEAD` state, and while Git doesn't care where you
Junio C Hamano8f62db92007-02-01 00:22:223916save the note about that state, in practice we tend to just write the
3917result to the file pointed at by `.git/HEAD`, so that we can always see
3918what the last committed state was.
3919
Junio C Hamanoe6f28d02013-09-17 21:34:003920Here is a picture that illustrates how various pieces fit together:
Junio C Hamano8f62db92007-02-01 00:22:223921
3922------------
3923
3924 commit-tree
3925 commit obj
3926 +----+
3927 | |
3928 | |
3929 V V
3930 +-----------+
3931 | Object DB |
3932 | Backing |
3933 | Store |
3934 +-----------+
3935 ^
3936 write-tree | |
3937 tree obj | |
3938 | | read-tree
3939 | | tree obj
3940 V
3941 +-----------+
3942 | Index |
3943 | "cache" |
3944 +-----------+
3945 update-index ^
3946 blob obj | |
3947 | |
3948 checkout-index -u | | checkout-index
3949 stat | | blob obj
3950 V
3951 +-----------+
3952 | Working |
3953 | Directory |
3954 +-----------+
3955
3956------------
3957
3958
Junio C Hamano3d30fd52007-05-08 00:32:533959[[examining-the-data]]
Junio C Hamano8f62db92007-02-01 00:22:223960Examining the data
3961------------------
3962
3963You can examine the data represented in the object database and the
3964index with various helper tools. For every object, you can use
Junio C Hamano35738e82008-01-07 07:55:463965linkgit:git-cat-file[1] to examine details about the
Junio C Hamano8f62db92007-02-01 00:22:223966object:
3967
3968-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:383969$ git cat-file -t <objectname>
Junio C Hamano8f62db92007-02-01 00:22:223970-------------------------------------------------
3971
3972shows the type of the object, and once you have the type (which is
3973usually implicit in where you find the object), you can use
3974
3975-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:383976$ git cat-file blob|tree|commit|tag <objectname>
Junio C Hamano8f62db92007-02-01 00:22:223977-------------------------------------------------
3978
3979to show its contents. NOTE! Trees have binary content, and as a result
3980there is a special helper for showing that content, called
Junio C Hamano5f9a6f02009-04-06 08:26:563981`git ls-tree`, which turns the binary content into a more easily
Junio C Hamano8f62db92007-02-01 00:22:223982readable form.
3983
3984It's especially instructive to look at "commit" objects, since those
3985tend to be small and fairly self-explanatory. In particular, if you
3986follow the convention of having the top commit name in `.git/HEAD`,
3987you can do
3988
3989-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:383990$ git cat-file commit HEAD
Junio C Hamano8f62db92007-02-01 00:22:223991-------------------------------------------------
3992
3993to see what the top commit was.
3994
Junio C Hamano3d30fd52007-05-08 00:32:533995[[merging-multiple-trees]]
Junio C Hamano8f62db92007-02-01 00:22:223996Merging multiple trees
3997----------------------
3998
Junio C Hamanoe6f28d02013-09-17 21:34:003999Git can help you perform a three-way merge, which can in turn be
4000used for a many-way merge by repeating the merge procedure several
4001times. The usual situation is that you only do one three-way merge
4002(reconciling two lines of history) and commit the result, but if
4003you like to, you can merge several branches in one go.
Junio C Hamano8f62db92007-02-01 00:22:224004
Junio C Hamanoe6f28d02013-09-17 21:34:004005To perform a three-way merge, you start with the two commits you
4006want to merge, find their closest common parent (a third commit),
4007and compare the trees corresponding to these three commits.
Junio C Hamano8f62db92007-02-01 00:22:224008
Junio C Hamanoe6f28d02013-09-17 21:34:004009To get the "base" for the merge, look up the common parent of two
4010commits:
Junio C Hamano8f62db92007-02-01 00:22:224011
4012-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:384013$ git merge-base <commit1> <commit2>
Junio C Hamano8f62db92007-02-01 00:22:224014-------------------------------------------------
4015
Junio C Hamanoe6f28d02013-09-17 21:34:004016This prints the name of a commit they are both based on. You should
4017now look up the tree objects of those commits, which you can easily
4018do with
Junio C Hamano8f62db92007-02-01 00:22:224019
4020-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:384021$ git cat-file commit <commitname> | head -1
Junio C Hamano8f62db92007-02-01 00:22:224022-------------------------------------------------
4023
4024since the tree object information is always the first line in a commit
4025object.
4026
4027Once you know the three trees you are going to merge (the one "original"
Junio C Hamano3d30fd52007-05-08 00:32:534028tree, aka the common tree, and the two "result" trees, aka the branches
Junio C Hamano8f62db92007-02-01 00:22:224029you want to merge), you do a "merge" read into the index. This will
4030complain if it has to throw away your old index contents, so you should
Junio C Hamano764a6672007-10-23 01:23:314031make sure that you've committed those--in fact you would normally
Junio C Hamano8f62db92007-02-01 00:22:224032always do a merge against your last commit (which should thus match what
4033you have in your current index anyway).
4034
4035To do the merge, do
4036
4037-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:384038$ git read-tree -m -u <origtree> <yourtree> <targettree>
Junio C Hamano8f62db92007-02-01 00:22:224039-------------------------------------------------
4040
4041which will do all trivial merge operations for you directly in the
4042index file, and you can just write the result out with
Junio C Hamanoba4b9282008-07-06 05:20:314043`git write-tree`.
Junio C Hamano8f62db92007-02-01 00:22:224044
4045
Junio C Hamano3d30fd52007-05-08 00:32:534046[[merging-multiple-trees-2]]
Junio C Hamano8f62db92007-02-01 00:22:224047Merging multiple trees, continued
4048---------------------------------
4049
4050Sadly, many merges aren't trivial. If there are files that have
Junio C Hamano764a6672007-10-23 01:23:314051been added, moved or removed, or if both branches have modified the
Junio C Hamano8f62db92007-02-01 00:22:224052same file, you will be left with an index tree that contains "merge
4053entries" in it. Such an index tree can 'NOT' be written out to a tree
4054object, and you will have to resolve any such merge clashes using
4055other tools before you can write out the result.
4056
Junio C Hamanofce7c7e2008-07-02 03:06:384057You can examine such index state with `git ls-files --unmerged`
Junio C Hamano8f62db92007-02-01 00:22:224058command. An example:
4059
4060------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:384061$ git read-tree -m $orig HEAD $target
4062$ git ls-files --unmerged
Junio C Hamano8f62db92007-02-01 00:22:224063100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
4064100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
4065100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c
4066------------------------------------------------
4067
Junio C Hamanofce7c7e2008-07-02 03:06:384068Each line of the `git ls-files --unmerged` output begins with
Junio C Hamano5f9a6f02009-04-06 08:26:564069the blob mode bits, blob SHA-1, 'stage number', and the
Junio C Hamano076ffcc2013-02-06 05:13:214070filename. The 'stage number' is Git's way to say which tree it
Junio C Hamano44dcd492012-07-24 04:35:384071came from: stage 1 corresponds to the `$orig` tree, stage 2 to
4072the `HEAD` tree, and stage 3 to the `$target` tree.
Junio C Hamano8f62db92007-02-01 00:22:224073
4074Earlier we said that trivial merges are done inside
Junio C Hamano5f9a6f02009-04-06 08:26:564075`git read-tree -m`. For example, if the file did not change
Junio C Hamanod75148a2014-04-08 19:48:384076from `$orig` to `HEAD` or `$target`, or if the file changed
Junio C Hamano8f62db92007-02-01 00:22:224077from `$orig` to `HEAD` and `$orig` to `$target` the same way,
4078obviously the final outcome is what is in `HEAD`. What the
4079above example shows is that file `hello.c` was changed from
4080`$orig` to `HEAD` and `$orig` to `$target` in a different way.
4081You could resolve this by running your favorite 3-way merge
Junio C Hamano076ffcc2013-02-06 05:13:214082program, e.g. `diff3`, `merge`, or Git's own merge-file, on
Junio C Hamano3d30fd52007-05-08 00:32:534083the blob objects from these three stages yourself, like this:
Junio C Hamano8f62db92007-02-01 00:22:224084
4085------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:384086$ git cat-file blob 263414f... >hello.c~1
4087$ git cat-file blob 06fa6a2... >hello.c~2
4088$ git cat-file blob cc44c73... >hello.c~3
Junio C Hamano3d30fd52007-05-08 00:32:534089$ git merge-file hello.c~2 hello.c~1 hello.c~3
Junio C Hamano8f62db92007-02-01 00:22:224090------------------------------------------------
4091
4092This would leave the merge result in `hello.c~2` file, along
4093with conflict markers if there are conflicts. After verifying
Junio C Hamano076ffcc2013-02-06 05:13:214094the merge result makes sense, you can tell Git what the final
Junio C Hamano8f62db92007-02-01 00:22:224095merge result for this file is by:
4096
4097-------------------------------------------------
4098$ mv -f hello.c~2 hello.c
Junio C Hamanofce7c7e2008-07-02 03:06:384099$ git update-index hello.c
Junio C Hamano8f62db92007-02-01 00:22:224100-------------------------------------------------
4101
Junio C Hamano5f9a6f02009-04-06 08:26:564102When a path is in the "unmerged" state, running `git update-index` for
Junio C Hamano076ffcc2013-02-06 05:13:214103that path tells Git to mark the path resolved.
Junio C Hamano8f62db92007-02-01 00:22:224104
Junio C Hamano076ffcc2013-02-06 05:13:214105The above is the description of a Git merge at the lowest level,
Junio C Hamano8f62db92007-02-01 00:22:224106to help you understand what conceptually happens under the hood.
Junio C Hamano076ffcc2013-02-06 05:13:214107In practice, nobody, not even Git itself, runs `git cat-file` three times
Junio C Hamano5f9a6f02009-04-06 08:26:564108for this. There is a `git merge-index` program that extracts the
Junio C Hamano8f62db92007-02-01 00:22:224109stages to temporary files and calls a "merge" script on it:
4110
4111-------------------------------------------------
Junio C Hamanofce7c7e2008-07-02 03:06:384112$ git merge-index git-merge-one-file hello.c
Junio C Hamano8f62db92007-02-01 00:22:224113-------------------------------------------------
4114
Junio C Hamano5f9a6f02009-04-06 08:26:564115and that is what higher level `git merge -s resolve` is implemented with.
Junio C Hamano8f62db92007-02-01 00:22:224116
Junio C Hamano597ffcf2007-09-17 17:33:154117[[hacking-git]]
Junio C Hamano076ffcc2013-02-06 05:13:214118Hacking Git
Junio C Hamano597ffcf2007-09-17 17:33:154119===========
Junio C Hamano8f62db92007-02-01 00:22:224120
Junio C Hamano076ffcc2013-02-06 05:13:214121This chapter covers internal details of the Git implementation which
4122probably only Git developers need to understand.
Junio C Hamano8f62db92007-02-01 00:22:224123
Junio C Hamano597ffcf2007-09-17 17:33:154124[[object-details]]
4125Object storage format
4126---------------------
Junio C Hamano8f62db92007-02-01 00:22:224127
Junio C Hamano597ffcf2007-09-17 17:33:154128All objects have a statically determined "type" which identifies the
4129format of the object (i.e. how it is used, and how it can refer to other
4130objects). There are currently four different object types: "blob",
4131"tree", "commit", and "tag".
Junio C Hamano8f62db92007-02-01 00:22:224132
Junio C Hamano597ffcf2007-09-17 17:33:154133Regardless of object type, all objects share the following
4134characteristics: they are all deflated with zlib, and have a header
4135that not only specifies their type, but also provides size information
Junio C Hamano5f9a6f02009-04-06 08:26:564136about the data in the object. It's worth noting that the SHA-1 hash
Junio C Hamano597ffcf2007-09-17 17:33:154137that is used to name the object is the hash of the original data
4138plus this header, so `sha1sum` 'file' does not match the object name
4139for 'file'.
Junio C Hamano8f62db92007-02-01 00:22:224140
Junio C Hamano597ffcf2007-09-17 17:33:154141As a result, the general consistency of an object can always be tested
4142independently of the contents or the type of the object: all objects can
4143be validated by verifying that (a) their hashes match the content of the
4144file and (b) the object successfully inflates to a stream of bytes that
Junio C Hamano947ab822013-03-19 23:07:294145forms a sequence of
4146`<ascii type without space> + <space> + <ascii decimal size> +
4147<byte\0> + <binary object data>`.
Junio C Hamano8f62db92007-02-01 00:22:224148
Junio C Hamano597ffcf2007-09-17 17:33:154149The structured objects can further have their structure and
4150connectivity to other objects verified. This is generally done with
Junio C Hamano5f9a6f02009-04-06 08:26:564151the `git fsck` program, which generates a full dependency graph
Junio C Hamano597ffcf2007-09-17 17:33:154152of all objects, and verifies their internal consistency (in addition
4153to just verifying their superficial consistency through the hash).
Junio C Hamano8f62db92007-02-01 00:22:224154
Junio C Hamano75485c82007-05-19 04:20:334155[[birdview-on-the-source-code]]
4156A birds-eye view of Git's source code
4157-------------------------------------
4158
4159It is not always easy for new developers to find their way through Git's
4160source code. This section gives you a little guidance to show where to
4161start.
4162
4163A good place to start is with the contents of the initial commit, with:
4164
4165----------------------------------------------------
4166$ git checkout e83c5163
4167----------------------------------------------------
4168
Junio C Hamano076ffcc2013-02-06 05:13:214169The initial revision lays the foundation for almost everything Git has
Junio C Hamano75485c82007-05-19 04:20:334170today, but is small enough to read in one sitting.
4171
4172Note that terminology has changed since that revision. For example, the
4173README in that revision uses the word "changeset" to describe what we
4174now call a <<def_commit_object,commit>>.
4175
Junio C Hamanod32738e2008-07-09 19:53:424176Also, we do not call it "cache" any more, but rather "index"; however, the
Junio C Hamano75485c82007-05-19 04:20:334177file is still called `cache.h`. Remark: Not much reason to change it now,
4178especially since there is no good single name for it anyway, because it is
4179basically _the_ header file which is included by _all_ of Git's C sources.
4180
4181If you grasp the ideas in that initial commit, you should check out a
4182more recent version and skim `cache.h`, `object.h` and `commit.h`.
4183
4184In the early days, Git (in the tradition of UNIX) was a bunch of programs
4185which were extremely simple, and which you used in scripts, piping the
4186output of one into another. This turned out to be good for initial
4187development, since it was easier to test new things. However, recently
4188many of these parts have become builtins, and some of the core has been
4189"libified", i.e. put into libgit.a for performance, portability reasons,
4190and to avoid code duplication.
4191
4192By now, you know what the index is (and find the corresponding data
4193structures in `cache.h`), and that there are just a couple of object types
4194(blobs, trees, commits and tags) which inherit their common structure from
4195`struct object`, which is their first member (and thus, you can cast e.g.
4196`(struct object *)commit` to achieve the _same_ as `&commit->object`, i.e.
4197get at the object name and flags).
4198
4199Now is a good point to take a break to let this information sink in.
4200
4201Next step: get familiar with the object naming. Read <<naming-commits>>.
4202There are quite a few ways to name an object (and not only revisions!).
4203All of these are handled in `sha1_name.c`. Just have a quick look at
4204the function `get_sha1()`. A lot of the special handling is done by
4205functions like `get_sha1_basic()` or the likes.
4206
4207This is just to get you into the groove for the most libified part of Git:
4208the revision walker.
4209
Junio C Hamano5f9a6f02009-04-06 08:26:564210Basically, the initial version of `git log` was a shell script:
Junio C Hamano75485c82007-05-19 04:20:334211
4212----------------------------------------------------------------
4213$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \
4214LESS=-S ${PAGER:-less}
4215----------------------------------------------------------------
4216
4217What does this mean?
4218
Junio C Hamano5f9a6f02009-04-06 08:26:564219`git rev-list` is the original version of the revision walker, which
Junio C Hamano75485c82007-05-19 04:20:334220_always_ printed a list of revisions to stdout. It is still functional,
Junio C Hamano27a128b2009-08-13 01:23:004221and needs to, since most new Git commands start out as scripts using
Junio C Hamano5f9a6f02009-04-06 08:26:564222`git rev-list`.
Junio C Hamano75485c82007-05-19 04:20:334223
Junio C Hamano5f9a6f02009-04-06 08:26:564224`git rev-parse` is not as important any more; it was only used to filter out
Junio C Hamano75485c82007-05-19 04:20:334225options that were relevant for the different plumbing commands that were
4226called by the script.
4227
Junio C Hamano5f9a6f02009-04-06 08:26:564228Most of what `git rev-list` did is contained in `revision.c` and
Junio C Hamano75485c82007-05-19 04:20:334229`revision.h`. It wraps the options in a struct named `rev_info`, which
4230controls how and what revisions are walked, and more.
4231
Junio C Hamano5f9a6f02009-04-06 08:26:564232The original job of `git rev-parse` is now taken by the function
Junio C Hamanoe1aeb5e2014-06-06 19:16:294233`setup_revisions()`, which parses the revisions and the common command-line
Junio C Hamano75485c82007-05-19 04:20:334234options for the revision walker. This information is stored in the struct
Junio C Hamanoe1aeb5e2014-06-06 19:16:294235`rev_info` for later consumption. You can do your own command-line option
Junio C Hamano75485c82007-05-19 04:20:334236parsing after calling `setup_revisions()`. After that, you have to call
4237`prepare_revision_walk()` for initialization, and then you can get the
4238commits one by one with the function `get_revision()`.
4239
4240If you are interested in more details of the revision walking process,
4241just have a look at the first implementation of `cmd_log()`; call
Junio C Hamanob76a6862012-05-02 22:02:464242`git show v1.3.0~155^2~4` and scroll down to that function (note that you
Junio C Hamano75485c82007-05-19 04:20:334243no longer need to call `setup_pager()` directly).
4244
Junio C Hamano5f9a6f02009-04-06 08:26:564245Nowadays, `git log` is a builtin, which means that it is _contained_ in the
Junio C Hamano75485c82007-05-19 04:20:334246command `git`. The source side of a builtin is
4247
Junio C Hamano3a3357e2013-06-26 23:20:564248- a function called `cmd_<bla>`, typically defined in `builtin/<bla.c>`
4249 (note that older versions of Git used to have it in `builtin-<bla>.c`
4250 instead), and declared in `builtin.h`.
Junio C Hamano75485c82007-05-19 04:20:334251
4252- an entry in the `commands[]` array in `git.c`, and
4253
4254- an entry in `BUILTIN_OBJECTS` in the `Makefile`.
4255
4256Sometimes, more than one builtin is contained in one source file. For
Junio C Hamano3a3357e2013-06-26 23:20:564257example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin/log.c`,
Junio C Hamano75485c82007-05-19 04:20:334258since they share quite a bit of code. In that case, the commands which are
4259_not_ named like the `.c` file in which they live have to be listed in
4260`BUILT_INS` in the `Makefile`.
4261
Junio C Hamano5f9a6f02009-04-06 08:26:564262`git log` looks more complicated in C than it does in the original script,
Junio C Hamano75485c82007-05-19 04:20:334263but that allows for a much greater flexibility and performance.
4264
4265Here again it is a good point to take a pause.
4266
4267Lesson three is: study the code. Really, it is the best way to learn about
4268the organization of Git (after you know the basic concepts).
4269
4270So, think about something which you are interested in, say, "how can I
4271access a blob just knowing the object name of it?". The first step is to
4272find a Git command with which you can do it. In this example, it is either
Junio C Hamano5f9a6f02009-04-06 08:26:564273`git show` or `git cat-file`.
Junio C Hamano75485c82007-05-19 04:20:334274
Junio C Hamano5f9a6f02009-04-06 08:26:564275For the sake of clarity, let's stay with `git cat-file`, because it
Junio C Hamano75485c82007-05-19 04:20:334276
4277- is plumbing, and
4278
4279- was around even in the initial commit (it literally went only through
Junio C Hamano3a3357e2013-06-26 23:20:564280 some 20 revisions as `cat-file.c`, was renamed to `builtin/cat-file.c`
Junio C Hamano75485c82007-05-19 04:20:334281 when made a builtin, and then saw less than 10 versions).
4282
Junio C Hamano3a3357e2013-06-26 23:20:564283So, look into `builtin/cat-file.c`, search for `cmd_cat_file()` and look what
Junio C Hamano75485c82007-05-19 04:20:334284it does.
4285
4286------------------------------------------------------------------
4287 git_config(git_default_config);
4288 if (argc != 3)
Junio C Hamano5f9a6f02009-04-06 08:26:564289usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>");
Junio C Hamano75485c82007-05-19 04:20:334290 if (get_sha1(argv[2], sha1))
4291 die("Not a valid object name %s", argv[2]);
4292------------------------------------------------------------------
4293
4294Let's skip over the obvious details; the only really interesting part
4295here is the call to `get_sha1()`. It tries to interpret `argv[2]` as an
4296object name, and if it refers to an object which is present in the current
4297repository, it writes the resulting SHA-1 into the variable `sha1`.
4298
4299Two things are interesting here:
4300
4301- `get_sha1()` returns 0 on _success_. This might surprise some new
4302 Git hackers, but there is a long tradition in UNIX to return different
Junio C Hamano764a6672007-10-23 01:23:314303 negative numbers in case of different errors--and 0 on success.
Junio C Hamano75485c82007-05-19 04:20:334304
4305- the variable `sha1` in the function signature of `get_sha1()` is `unsigned
Junio C Hamanob76a6862012-05-02 22:02:464306 char *`, but is actually expected to be a pointer to `unsigned
Junio C Hamano75485c82007-05-19 04:20:334307 char[20]`. This variable will contain the 160-bit SHA-1 of the given
Junio C Hamanob76a6862012-05-02 22:02:464308 commit. Note that whenever a SHA-1 is passed as `unsigned char *`, it
Junio C Hamano75485c82007-05-19 04:20:334309 is the binary representation, as opposed to the ASCII representation in
4310 hex characters, which is passed as `char *`.
4311
4312You will see both of these things throughout the code.
4313
4314Now, for the meat:
4315
4316-----------------------------------------------------------------------------
4317 case 0:
4318 buf = read_object_with_reference(sha1, argv[1], &size, NULL);
4319-----------------------------------------------------------------------------
4320
4321This is how you read a blob (actually, not only a blob, but any type of
4322object). To know how the function `read_object_with_reference()` actually
4323works, find the source code for it (something like `git grep
Junio C Hamano076ffcc2013-02-06 05:13:214324read_object_with | grep ":[a-z]"` in the Git repository), and read
Junio C Hamano75485c82007-05-19 04:20:334325the source.
4326
4327To find out how the result can be used, just read on in `cmd_cat_file()`:
4328
4329-----------------------------------
4330 write_or_die(1, buf, size);
4331-----------------------------------
4332
4333Sometimes, you do not know where to look for a feature. In many such cases,
Junio C Hamano5f9a6f02009-04-06 08:26:564334it helps to search through the output of `git log`, and then `git show` the
Junio C Hamano75485c82007-05-19 04:20:334335corresponding commit.
4336
Junio C Hamano5f9a6f02009-04-06 08:26:564337Example: If you know that there was some test case for `git bundle`, but
Junio C Hamano75485c82007-05-19 04:20:334338do not remember where it was (yes, you _could_ `git grep bundle t/`, but that
4339does not illustrate the point!):
4340
4341------------------------
4342$ git log --no-merges t/
4343------------------------
4344
4345In the pager (`less`), just search for "bundle", go a few lines back,
4346and see that it is in commit 18449ab0... Now just copy this object name,
4347and paste it into the command line
4348
4349-------------------
4350$ git show 18449ab0
4351-------------------
4352
4353Voila.
4354
4355Another example: Find out what to do in order to make some script a
4356builtin:
4357
4358-------------------------------------------------
Junio C Hamano3a3357e2013-06-26 23:20:564359$ git log --no-merges --diff-filter=A builtin/*.c
Junio C Hamano75485c82007-05-19 04:20:334360-------------------------------------------------
4361
4362You see, Git is actually the best tool to find out about the source of Git
4363itself!
4364
Junio C Hamano3d30fd52007-05-08 00:32:534365[[glossary]]
Junio C Hamanobf984de2009-11-23 06:11:194366Git Glossary
Junio C Hamano9e1793f2008-06-02 07:31:164367============
4368
4369include::glossary-content.txt[]
Junio C Hamano8f62db92007-02-01 00:22:224370
Junio C Hamano75485c82007-05-19 04:20:334371[[git-quick-start]]
Junio C Hamanof614c642007-06-11 01:21:544372Appendix A: Git Quick Reference
4373===============================
Junio C Hamano75485c82007-05-19 04:20:334374
Junio C Hamanof614c642007-06-11 01:21:544375This is a quick summary of the major commands; the previous chapters
4376explain how these work in more detail.
Junio C Hamano75485c82007-05-19 04:20:334377
4378[[quick-creating-a-new-repository]]
4379Creating a new repository
4380-------------------------
4381
4382From a tarball:
4383
4384-----------------------------------------------
4385$ tar xzf project.tar.gz
4386$ cd project
4387$ git init
4388Initialized empty Git repository in .git/
4389$ git add .
4390$ git commit
4391-----------------------------------------------
4392
4393From a remote repository:
4394
4395-----------------------------------------------
4396$ git clone git://example.com/pub/project.git
4397$ cd project
4398-----------------------------------------------
4399
4400[[managing-branches]]
4401Managing branches
4402-----------------
4403
4404-----------------------------------------------
4405$ git branch # list all local branches in this repo
4406$ git checkout test # switch working directory to branch "test"
4407$ git branch new # create branch "new" starting at current HEAD
4408$ git branch -d new # delete branch "new"
4409-----------------------------------------------
4410
Junio C Hamano764a6672007-10-23 01:23:314411Instead of basing a new branch on current HEAD (the default), use:
Junio C Hamano75485c82007-05-19 04:20:334412
4413-----------------------------------------------
4414$ git branch new test # branch named "test"
4415$ git branch new v2.6.15 # tag named v2.6.15
4416$ git branch new HEAD^ # commit before the most recent
4417$ git branch new HEAD^^ # commit before that
4418$ git branch new test~10 # ten commits before tip of branch "test"
4419-----------------------------------------------
4420
4421Create and switch to a new branch at the same time:
4422
4423-----------------------------------------------
4424$ git checkout -b new v2.6.15
4425-----------------------------------------------
4426
4427Update and examine branches from the repository you cloned from:
4428
4429-----------------------------------------------
4430$ git fetch # update
4431$ git branch -r # list
4432 origin/master
4433 origin/next
4434 ...
4435$ git checkout -b masterwork origin/master
4436-----------------------------------------------
4437
4438Fetch a branch from a different repository, and give it a new
4439name in your repository:
4440
4441-----------------------------------------------
4442$ git fetch git://example.com/project.git theirbranch:mybranch
4443$ git fetch git://example.com/project.git v2.6.15:mybranch
4444-----------------------------------------------
4445
4446Keep a list of repositories you work with regularly:
4447
4448-----------------------------------------------
4449$ git remote add example git://example.com/project.git
4450$ git remote # list remote repositories
4451example
4452origin
4453$ git remote show example # get details
4454* remote example
4455 URL: git://example.com/project.git
4456 Tracked remote branches
Junio C Hamanoedc174c2008-10-23 05:18:544457 master
4458 next
4459 ...
Junio C Hamano75485c82007-05-19 04:20:334460$ git fetch example # update branches from example
4461$ git branch -r # list all remote branches
4462-----------------------------------------------
4463
4464
4465[[exploring-history]]
4466Exploring history
4467-----------------
4468
4469-----------------------------------------------
4470$ gitk # visualize and browse history
4471$ git log # list all commits
4472$ git log src/ # ...modifying src/
4473$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
4474$ git log master..test # ...in branch test, not in branch master
4475$ git log test..master # ...in branch master, but not in test
4476$ git log test...master # ...in one branch, not in both
4477$ git log -S'foo()' # ...where difference contain "foo()"
4478$ git log --since="2 weeks ago"
4479$ git log -p # show patches as well
4480$ git show # most recent commit
4481$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
4482$ git diff v2.6.15..HEAD # diff with current head
4483$ git grep "foo()" # search working directory for "foo()"
4484$ git grep v2.6.15 "foo()" # search old tree for "foo()"
4485$ git show v2.6.15:a.txt # look at old version of a.txt
4486-----------------------------------------------
4487
4488Search for regressions:
4489
4490-----------------------------------------------
4491$ git bisect start
4492$ git bisect bad # current version is bad
4493$ git bisect good v2.6.13-rc2 # last known good revision
4494Bisecting: 675 revisions left to test after this
4495# test here, then:
4496$ git bisect good # if this revision is good, or
4497$ git bisect bad # if this revision is bad.
4498# repeat until done.
4499-----------------------------------------------
4500
4501[[making-changes]]
4502Making changes
4503--------------
4504
Junio C Hamano076ffcc2013-02-06 05:13:214505Make sure Git knows who to blame:
Junio C Hamano75485c82007-05-19 04:20:334506
4507------------------------------------------------
4508$ cat >>~/.gitconfig <<\EOF
4509[user]
4510name = Your Name Comes Here
4511email = you@yourdomain.example.com
4512EOF
4513------------------------------------------------
4514
4515Select file contents to include in the next commit, then make the
4516commit:
4517
4518-----------------------------------------------
4519$ git add a.txt # updated file
4520$ git add b.txt # new file
4521$ git rm c.txt # old file
4522$ git commit
4523-----------------------------------------------
4524
4525Or, prepare and create the commit in one step:
4526
4527-----------------------------------------------
4528$ git commit d.txt # use latest content only of d.txt
4529$ git commit -a # use latest content of all tracked files
4530-----------------------------------------------
4531
4532[[merging]]
4533Merging
4534-------
4535
4536-----------------------------------------------
4537$ git merge test # merge branch "test" into the current branch
4538$ git pull git://example.com/project.git master
4539 # fetch and merge in remote branch
4540$ git pull . test # equivalent to git merge test
4541-----------------------------------------------
4542
4543[[sharing-your-changes]]
4544Sharing your changes
4545--------------------
4546
4547Importing or exporting patches:
4548
4549-----------------------------------------------
4550$ git format-patch origin..HEAD # format a patch for each commit
4551# in HEAD but not in origin
4552$ git am mbox # import patches from the mailbox "mbox"
4553-----------------------------------------------
4554
Junio C Hamano076ffcc2013-02-06 05:13:214555Fetch a branch in a different Git repository, then merge into the
Junio C Hamano75485c82007-05-19 04:20:334556current branch:
4557
4558-----------------------------------------------
4559$ git pull git://example.com/project.git theirbranch
4560-----------------------------------------------
4561
4562Store the fetched branch into a local branch before merging into the
4563current branch:
4564
4565-----------------------------------------------
4566$ git pull git://example.com/project.git theirbranch:mybranch
4567-----------------------------------------------
4568
4569After creating commits on a local branch, update the remote
4570branch with your commits:
4571
4572-----------------------------------------------
4573$ git push ssh://example.com/project.git mybranch:theirbranch
4574-----------------------------------------------
4575
4576When remote and local branch are both named "test":
4577
4578-----------------------------------------------
4579$ git push ssh://example.com/project.git test
4580-----------------------------------------------
4581
4582Shortcut version for a frequently used remote repository:
4583
4584-----------------------------------------------
4585$ git remote add example ssh://example.com/project.git
4586$ git push example test
4587-----------------------------------------------
4588
4589[[repository-maintenance]]
4590Repository maintenance
4591----------------------
4592
4593Check for corruption:
4594
4595-----------------------------------------------
4596$ git fsck
4597-----------------------------------------------
4598
4599Recompress, remove unused cruft:
4600
4601-----------------------------------------------
4602$ git gc
4603-----------------------------------------------
4604
4605
Junio C Hamano3d30fd52007-05-08 00:32:534606[[todo]]
Junio C Hamano75485c82007-05-19 04:20:334607Appendix B: Notes and todo list for this manual
4608===============================================
Junio C Hamano8f62db92007-02-01 00:22:224609
4610This is a work in progress.
4611
4612The basic requirements:
Junio C Hamano597ffcf2007-09-17 17:33:154613
4614- It must be readable in order, from beginning to end, by someone
4615 intelligent with a basic grasp of the UNIX command line, but without
Junio C Hamano076ffcc2013-02-06 05:13:214616 any special knowledge of Git. If necessary, any other prerequisites
Junio C Hamano597ffcf2007-09-17 17:33:154617 should be specifically mentioned as they arise.
4618- Whenever possible, section headings should clearly describe the task
4619 they explain how to do, in language that requires no more knowledge
4620 than necessary: for example, "importing patches into a project" rather
Junio C Hamano5f9a6f02009-04-06 08:26:564621 than "the `git am` command"
Junio C Hamano8f62db92007-02-01 00:22:224622
4623Think about how to create a clear chapter dependency graph that will
4624allow people to get to important topics without necessarily reading
4625everything in between.
4626
Junio C Hamano947ab822013-03-19 23:07:294627Scan `Documentation/` for other stuff left out; in particular:
Junio C Hamano597ffcf2007-09-17 17:33:154628
4629- howto's
Junio C Hamano947ab822013-03-19 23:07:294630- some of `technical/`?
Junio C Hamano597ffcf2007-09-17 17:33:154631- hooks
Junio C Hamano35738e82008-01-07 07:55:464632- list of commands in linkgit:git[1]
Junio C Hamano8f62db92007-02-01 00:22:224633
4634Scan email archives for other stuff left out
4635
4636Scan man pages to see if any assume more background than this manual
4637provides.
4638
4639Simplify beginning by suggesting disconnected head instead of
4640temporary branch creation?
4641
Junio C Hamano8f62db92007-02-01 00:22:224642Add more good examples. Entire sections of just cookbook examples
4643might be a good idea; maybe make an "advanced examples" section a
4644standard end-of-chapter section?
4645
4646Include cross-references to the glossary, where appropriate.
4647
4648Document shallow clones? See draft 1.5.0 release notes for some
4649documentation.
4650
Junio C Hamanoee1e4282007-02-04 08:32:044651Add a section on working with other version control systems, including
Junio C Hamano8f62db92007-02-01 00:22:224652CVS, Subversion, and just imports of series of release tarballs.
4653
4654More details on gitweb?
4655
4656Write a chapter on using plumbing and writing scripts.
Junio C Hamanof614c642007-06-11 01:21:544657
4658Alternates, clone -reference, etc.
4659
Junio C Hamanoce3650e2007-11-26 04:20:114660More on recovery from repository corruption. See:
Junio C Hamano58f587a2013-07-22 19:20:594661http://marc.info/?l=git&m=117263864820799&w=2
4662http://marc.info/?l=git&m=117147855503798&w=2