Documentation/user-manual: update outdated example output
[git/git.git] / Documentation / user-manual.txt
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333d7d37 1Git User Manual
145e073b 2===============
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3
4Git is a fast distributed revision control system.
5
02783075 6This manual is designed to be readable by someone with basic UNIX
2de9b711 7command-line skills, but no previous knowledge of Git.
d19fbc3c 8
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9<<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.
ef89f701 13
2624d9a5 14People needing to do actual development will also want to read
aa971cb9 15<<Developing-With-git>> and <<sharing-development>>.
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16
17Further chapters cover more specialized topics.
18
d19fbc3c 19Comprehensive reference documentation is available through the man
b3d98887 20pages, or linkgit:git-help[1] command. For example, for the command
1249d8ad 21`git clone <repo>`, you can either use:
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22
23------------------------------------------------
24$ man git-clone
25------------------------------------------------
26
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27or:
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
2de9b711 36See also <<git-quick-start>> for a brief overview of Git commands,
2624d9a5 37without any explanation.
b181d57f 38
99f171bb 39Finally, see <<todo>> for ways that you can help make this manual more
2624d9a5 40complete.
b181d57f 41
b181d57f 42
e34caace 43[[repositories-and-branches]]
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44Repositories and Branches
45=========================
46
e34caace 47[[how-to-get-a-git-repository]]
2de9b711 48How to get a Git repository
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49---------------------------
50
2de9b711 51It will be useful to have a Git repository to experiment with as you
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52read this manual.
53
5162e697 54The best way to get one is by using the linkgit:git-clone[1] command to
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55download a copy of an existing repository. If you don't already have a
56project in mind, here are some interesting examples:
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57
58------------------------------------------------
4b9ced27 59 # Git itself (approx. 40MB download):
d19fbc3c 60$ git clone git://git.kernel.org/pub/scm/git/git.git
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61 # the Linux kernel (approx. 640MB download):
62$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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63------------------------------------------------
64
65The initial clone may be time-consuming for a large project, but you
66will only need to clone once.
67
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68The clone command creates a new directory named after the project
69(`git` or `linux` in the examples above). After you cd into this
d19fbc3c 70directory, you will see that it contains a copy of the project files,
0c4a33b5 71called the <<def_working_tree,working tree>>, together with a special
1249d8ad 72top-level directory named `.git`, which contains all the information
0c4a33b5 73about the history of the project.
d19fbc3c 74
e34caace 75[[how-to-check-out]]
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76How to check out a different version of a project
77-------------------------------------------------
78
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79Git 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
2de9b711 81interrelated snapshots of the project's contents. In Git each such
a2ef9d63 82version is called a <<def_commit,commit>>.
d19fbc3c 83
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84Those snapshots aren't necessarily all arranged in a single line from
85oldest to newest; instead, work may simultaneously proceed along
57283291 86parallel lines of development, called <<def_branch,branches>>, which may
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87merge and diverge.
88
2de9b711 89A single Git repository can track development on multiple branches. It
0c4a33b5 90does this by keeping a list of <<def_head,heads>> which reference the
5162e697 91latest commit on each branch; the linkgit:git-branch[1] command shows
81b6c950 92you the list of branch heads:
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93
94------------------------------------------------
95$ git branch
96* master
97------------------------------------------------
98
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99A 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.
d19fbc3c 102
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103Most projects also use <<def_tag,tags>>. Tags, like heads, are
104references into the project's history, and can be listed using the
5162e697 105linkgit:git-tag[1] command:
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106
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
fe4b3e59 121Tags are expected to always point at the same version of a project,
81b6c950 122while heads are expected to advance as development progresses.
fe4b3e59 123
81b6c950 124Create a new branch head pointing to one of these versions and check it
5162e697 125out using linkgit:git-checkout[1]:
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126
127------------------------------------------------
128$ git checkout -b new v2.6.13
129------------------------------------------------
130
131The working directory then reflects the contents that the project had
5162e697 132when it was tagged v2.6.13, and linkgit:git-branch[1] shows two
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133branches, 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
81b6c950 148Note that if the current branch head was your only reference to a
d19fbc3c 149particular point in history, then resetting that branch may leave you
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150with no way to find the history it used to point to; so use this command
151carefully.
d19fbc3c 152
e34caace 153[[understanding-commits]]
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154Understanding History: Commits
155------------------------------
156
157Every change in the history of a project is represented by a commit.
5162e697 158The linkgit:git-show[1] command shows the most recent commit on the
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159current branch:
160
161------------------------------------------------
162$ git show
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163commit 17cf781661e6d38f737f15f53ab552f1e95960d7
164Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)>
165Date: Tue Apr 19 14:11:06 2005 -0700
166
167 Remove duplicate getenv(DB_ENVIRONMENT) call
168
169 Noted by Tony Luck.
170
171diff --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 @@
d19fbc3c 176
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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) {
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184------------------------------------------------
185
186As you can see, a commit shows who made the latest change, what they
187did, and why.
188
35121930 189Every commit has a 40-hexdigit id, sometimes called the "object name" or the
1249d8ad 190"SHA-1 id", shown on the first line of the `git show` output. You can usually
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191refer 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
2de9b711 200In fact, in <<git-concepts>> we shall see that everything stored in Git
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201history, including file data and directory contents, is stored in an object
202with a name that is a hash of its contents.
d19fbc3c 203
e34caace 204[[understanding-reachability]]
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205Understanding 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
2de9b711 213However, the commits do not form a simple list; Git allows lines of
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214development 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
5162e697 220The best way to see how this works is using the linkgit:gitk[1]
2de9b711 221command; running gitk now on a Git repository and looking for merge
ddd4ddef 222commits will help understand how Git organizes history.
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223
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
02783075 226that Y is a descendant of X, or that there is a chain of parents
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227leading from commit Y to commit X.
228
e34caace 229[[history-diagrams]]
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230Understanding history: History diagrams
231~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 232
2de9b711 233We will sometimes represent Git history using diagrams like the one
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234below. Commits are shown as "o", and the links between them with
235lines drawn with - / and \. Time goes left to right:
236
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237
238................................................
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239 o--o--o <-- Branch A
240 /
241 o--o--o <-- master
242 \
243 o--o--o <-- Branch B
1dc71a91 244................................................
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245
246If we need to talk about a particular commit, the character "o" may
247be replaced with another letter or number.
248
e34caace 249[[what-is-a-branch]]
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250Understanding history: What is a branch?
251~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
252
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253When 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
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258"branch A".
259
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260However, when no confusion will result, we often just use the term
261"branch" both for branches and for branch heads.
d19fbc3c 262
e34caace 263[[manipulating-branches]]
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264Manipulating branches
265---------------------
266
267Creating, deleting, and modifying branches is quick and easy; here's
268a summary of the commands:
269
1249d8ad 270`git branch`::
df47da75 271 list all branches.
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272`git branch <branch>`::
273 create a new branch named `<branch>`, referencing the same
df47da75 274 point in history as the current branch.
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275`git branch <branch> <start-point>`::
276 create a new branch named `<branch>`, referencing
277 `<start-point>`, which may be specified any way you like,
df47da75 278 including using a branch name or a tag name.
1249d8ad 279`git branch -d <branch>`::
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280 delete the branch `<branch>`; if the branch is not fully
281 merged in its upstream branch or contained in the current branch,
282 this command will fail with a warning.
1249d8ad 283`git branch -D <branch>`::
df47da75 284 delete the branch `<branch>` irrespective of its merged status.
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285`git checkout <branch>`::
286 make the current branch `<branch>`, updating the working
df47da75 287 directory to reflect the version referenced by `<branch>`.
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288`git checkout -b <new> <start-point>`::
289 create a new branch `<new>` referencing `<start-point>`, and
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290 check it out.
291
72a76c95 292The special symbol "HEAD" can always be used to refer to the current
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293branch. In fact, Git uses a file named `HEAD` in the `.git` directory
294to remember which branch is current:
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295
296------------------------------------------------
297$ cat .git/HEAD
298ref: refs/heads/master
299------------------------------------------------
300
25d9f3fa 301[[detached-head]]
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302Examining an old version without creating a new branch
303------------------------------------------------------
304
6127c086 305The `git checkout` command normally expects a branch head, but will also
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306accept an arbitrary commit; for example, you can check out the commit
307referenced by a tag:
308
309------------------------------------------------
310$ git checkout v2.6.17
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311Note: 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
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322HEAD is now at 427abfa... Linux v2.6.17
323------------------------------------------------
324
a6e5ef7d 325The HEAD then refers to the SHA-1 of the commit instead of to a branch,
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326and git branch shows that you are no longer on a branch:
327
328------------------------------------------------
329$ cat .git/HEAD
330427abfa28afedffadfca9dd8b067eb6d36bac53f
953f3d6f 331$ git branch
95f9be55 332* (detached from v2.6.17)
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333 master
334------------------------------------------------
335
336In this case we say that the HEAD is "detached".
337
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338This 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.
d19fbc3c 341
e34caace 342[[examining-remote-branches]]
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343Examining 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
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349keeps branches which track each of those remote branches, called
350remote-tracking branches, which you
1249d8ad 351can view using the `-r` option to linkgit:git-branch[1]:
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352
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
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365In 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
1249d8ad 369be updated by `git fetch` (hence `git pull`) and `git push`. See
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370<<Updating-a-repository-With-git-fetch>> for details.
371
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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:
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374
375------------------------------------------------
376$ git checkout -b my-todo-copy origin/todo
377------------------------------------------------
378
1249d8ad 379You can also check out `origin/todo` directly to examine it or
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380write a one-off patch. See <<detached-head,detached head>>.
381
2de9b711 382Note that the name "origin" is just the name that Git uses by default
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383to refer to the repository that you cloned from.
384
385[[how-git-stores-references]]
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386Naming branches, tags, and other references
387-------------------------------------------
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388
389Branches, remote-tracking branches, and tags are all references to
f60b9642 390commits. All references are named with a slash-separated path name
1249d8ad 391starting with `refs`; the names we've been using so far are actually
f60b9642 392shorthand:
d19fbc3c 393
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394 - 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`.
d19fbc3c 397
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398The full name is occasionally useful if, for example, there ever
399exists a tag and a branch with the same name.
d19fbc3c 400
1249d8ad 401(Newly created refs are actually stored in the `.git/refs` directory,
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402under the path given by their name. However, for efficiency reasons
403they may also be packed together in a single file; see
5162e697 404linkgit:git-pack-refs[1]).
fc74ecc1 405
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406As 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".
d19fbc3c 409
2de9b711 410For the complete list of paths which Git checks for references, and
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411the order it uses to decide which to choose when there are multiple
412references with the same shorthand name, see the "SPECIFYING
9d83e382 413REVISIONS" section of linkgit:gitrevisions[7].
d19fbc3c 414
aa971cb9 415[[Updating-a-repository-With-git-fetch]]
6127c086 416Updating a repository with git fetch
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417------------------------------------
418
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419After you clone a repository and commit a few changes of your own, you
420may wish to check the original repository for updates.
d19fbc3c 421
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422The `git-fetch` command, with no arguments, will update all of the
423remote-tracking branches to the latest version found in the original
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424repository. It will not touch any of your own branches--not even the
425"master" branch that was created for you on clone.
426
e34caace 427[[fetching-branches]]
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428Fetching branches from other repositories
429-----------------------------------------
430
431You can also track branches from repositories other than the one you
5162e697 432cloned from, using linkgit:git-remote[1]:
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433
434-------------------------------------------------
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435$ 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
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442-------------------------------------------------
443
444New remote-tracking branches will be stored under the shorthand name
34a25d4c 445that you gave `git remote add`, in this case `staging`:
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446
447-------------------------------------------------
448$ git branch -r
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449 origin/HEAD -> origin/master
450 origin/master
451 staging/master
452 staging/staging-linus
453 staging/staging-next
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454-------------------------------------------------
455
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456If you run `git fetch <remote>` later, the remote-tracking branches
457for the named `<remote>` will be updated.
d5cd5de4 458
1249d8ad 459If you examine the file `.git/config`, you will see that Git has added
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460a new stanza:
461
462-------------------------------------------------
463$ cat .git/config
464...
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465[remote "staging"]
466 url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
467 fetch = +refs/heads/*:refs/remotes/staging/*
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468...
469-------------------------------------------------
470
2de9b711 471This is what causes Git to track the remote's branches; you may modify
1249d8ad 472or delete these configuration options by editing `.git/config` with a
fc90c536 473text editor. (See the "CONFIGURATION FILE" section of
5162e697 474linkgit:git-config[1] for details.)
d5cd5de4 475
e34caace 476[[exploring-git-history]]
2de9b711 477Exploring Git history
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478=====================
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
1130845b 482the contents of a file hierarchy, together with "commits" which show
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483the relationships between these snapshots.
484
485Git provides extremely flexible and fast tools for exploring the
486history of a project.
487
aacd404e 488We start with one specialized tool that is useful for finding the
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489commit that introduced a bug into a project.
490
e34caace 491[[using-bisect]]
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492How 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
5162e697 499linkgit:git-bisect[1] command can help you do this:
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500
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
1249d8ad 509If you run `git branch` at this point, you'll see that Git has
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510temporarily 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:
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514
515-------------------------------------------------
516$ git bisect bad
517Bisecting: 1769 revisions left to test after this
518[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
519-------------------------------------------------
520
2de9b711 521checks out an older version. Continue like this, telling Git at each
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522stage 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
5162e697 528linkgit:git-show[1], find out who wrote it, and mail them your bug
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529report with the commit id. Finally, run
530
531-------------------------------------------------
532$ git bisect reset
533-------------------------------------------------
534
0e25790f 535to return you to the branch you were on before.
d19fbc3c 536
6127c086 537Note that the version which `git bisect` checks out for you at each
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538point 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-------------------------------------------------
04483524 544$ git bisect visualize
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545-------------------------------------------------
546
547which will run gitk and label the commit it chose with a marker that
843c81dc 548says "bisect". Choose a safe-looking commit nearby, note its commit
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549id, and check it out with:
550
551-------------------------------------------------
552$ git reset --hard fb47ddb2db...
553-------------------------------------------------
554
1249d8ad 555then test, run `bisect good` or `bisect bad` as appropriate, and
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556continue.
557
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558Instead of `git bisect visualize` and then `git reset --hard
559fb47ddb2db...`, you might just want to tell Git that you want to skip
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560the current commit:
561
562-------------------------------------------------
563$ git bisect skip
564-------------------------------------------------
565
2de9b711 566In this case, though, Git may not eventually be able to tell the first
a0178ae2 567bad one between some first skipped commits and a later bad commit.
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568
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
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571linkgit:git-bisect[1] for more information about this and other `git
572bisect` features.
0e25790f 573
e34caace 574[[naming-commits]]
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575Naming commits
576--------------
577
578We have seen several ways of naming commits already:
579
d55ae921 580 - 40-hexdigit object name
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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
eb6ae7f4 588There are many more; see the "SPECIFYING REVISIONS" section of the
9d83e382 589linkgit:gitrevisions[7] man page for the complete list of ways to
d19fbc3c
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590name revisions. Some examples:
591
592-------------------------------------------------
d55ae921 593$ git show fb47ddb2 # the first few characters of the object name
d19fbc3c
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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,
1249d8ad 601`^` and `~` follow the first parent listed in the commit, but you can
d19fbc3c
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602also 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
6127c086 613`git reset`, which change the currently checked-out commit, generally
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614set ORIG_HEAD to the value HEAD had before the current operation.
615
6127c086
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616The `git fetch` operation always stores the head of the last fetched
617branch in FETCH_HEAD. For example, if you run `git fetch` without
d19fbc3c
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618specifying 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
5162e697 630The linkgit:git-rev-parse[1] command is a low-level command that is
d55ae921
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631occasionally useful for translating some name for a commit to the object
632name for that commit:
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633
634-------------------------------------------------
635$ git rev-parse origin
636e05db0fd4f31dde7005f075a84f96b360d05984b
637-------------------------------------------------
638
e34caace 639[[creating-tags]]
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640Creating tags
641-------------
642
643We can also create a tag to refer to a particular commit; after
644running
645
646-------------------------------------------------
04483524 647$ git tag stable-1 1b2e1d63ff
d19fbc3c
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648-------------------------------------------------
649
1249d8ad 650You can use `stable-1` to refer to the commit 1b2e1d63ff.
d19fbc3c 651
c64415e2
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652This creates a "lightweight" tag. If you would also like to include a
653comment with the tag, and possibly sign it cryptographically, then you
5162e697 654should create a tag object instead; see the linkgit:git-tag[1] man page
c64415e2 655for details.
d19fbc3c 656
e34caace 657[[browsing-revisions]]
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658Browsing revisions
659------------------
660
5162e697 661The linkgit:git-log[1] command can show lists of commits. On its
d19fbc3c
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662own, 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
1249d8ad 679commits since v2.5 which touch the `Makefile` or any file under `fs`:
d19fbc3c
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680
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
1249d8ad 691See the `--pretty` option in the linkgit:git-log[1] man page for more
d19fbc3c
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692display options.
693
694Note that git log starts with the most recent commit and works
2de9b711 695backwards through the parents; however, since Git history can contain
3dff5379 696multiple independent lines of development, the particular order that
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697commits are listed in may be somewhat arbitrary.
698
e34caace 699[[generating-diffs]]
d19fbc3c
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700Generating diffs
701----------------
702
703You can generate diffs between any two versions using
5162e697 704linkgit:git-diff[1]:
d19fbc3c
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705
706-------------------------------------------------
707$ git diff master..test
708-------------------------------------------------
709
5b98d9bc
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710That 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
5162e697 719use linkgit:git-format-patch[1]:
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720
721-------------------------------------------------
722$ git format-patch master..test
723-------------------------------------------------
724
725will generate a file with a patch for each commit reachable from test
5b98d9bc 726but not from master.
d19fbc3c 727
e34caace 728[[viewing-old-file-versions]]
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729Viewing 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
2de9b711 742may be any path to a file tracked by Git.
d19fbc3c 743
e34caace 744[[history-examples]]
aec053bb
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745Examples
746--------
747
46acd3fa
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748[[counting-commits-on-a-branch]]
749Counting the number of commits on a branch
750~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
751
1249d8ad
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752Suppose you want to know how many commits you've made on `mybranch`
753since it diverged from `origin`:
46acd3fa
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754
755-------------------------------------------------
756$ git log --pretty=oneline origin..mybranch | wc -l
757-------------------------------------------------
758
759Alternatively, you may often see this sort of thing done with the
a6e5ef7d 760lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's
46acd3fa
BF
761of all the given commits:
762
763-------------------------------------------------
764$ git rev-list origin..mybranch | wc -l
765-------------------------------------------------
766
e34caace 767[[checking-for-equal-branches]]
aec053bb 768Check whether two branches point at the same history
2f99710c 769~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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
69f7ad73
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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
d55ae921 781routes. You could compare the object names:
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782
783-------------------------------------------------
784$ git rev-list origin
785e05db0fd4f31dde7005f075a84f96b360d05984b
786$ git rev-list master
787e05db0fd4f31dde7005f075a84f96b360d05984b
788-------------------------------------------------
789
1249d8ad 790Or you could recall that the `...` operator selects all commits
ddd4ddef 791reachable from either one reference or the other but not
ddd2369c 792both; so
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793
794-------------------------------------------------
795$ git log origin...master
796-------------------------------------------------
797
798will return no commits when the two branches are equal.
799
e34caace 800[[finding-tagged-descendants]]
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801Find first tagged version including a given fix
802~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
aec053bb 803
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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
ddd4ddef 818or you can use linkgit:git-name-rev[1], which will give the commit a
b181d57f
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819name based on any tag it finds pointing to one of the commit's
820descendants:
821
822-------------------------------------------------
04483524 823$ git name-rev --tags e05db0fd
b181d57f
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824e05db0fd tags/v1.5.0-rc1^0~23
825-------------------------------------------------
826
5162e697 827The linkgit:git-describe[1] command does the opposite, naming the
b181d57f
BF
828revision using a tag on which the given commit is based:
829
830-------------------------------------------------
831$ git describe e05db0fd
04483524 832v1.5.0-rc0-260-ge05db0f
b181d57f
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833-------------------------------------------------
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
5162e697 839given commit, you could use linkgit:git-merge-base[1]:
b181d57f
BF
840
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-------------------------------------------------
4a7979ca 854$ git log v1.5.0-rc1..e05db0fd
b181d57f
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855-------------------------------------------------
856
4a7979ca 857will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
b181d57f 858because it outputs only commits that are not reachable from v1.5.0-rc1.
aec053bb 859
5162e697 860As yet another alternative, the linkgit:git-show-branch[1] command lists
4a7979ca 861the commits reachable from its arguments with a display on the left-hand
ddd4ddef
TA
862side that indicates which arguments that commit is reachable from.
863So, if you run something like
4a7979ca
BF
864
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
ddd4ddef 875then a line like
4a7979ca
BF
876
877-------------------------------------------------
878+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
879available
880-------------------------------------------------
881
ddd4ddef
TA
882shows that e05db0fd is reachable from itself, from v1.5.0-rc1,
883and from v1.5.0-rc2, and not from v1.5.0-rc0.
4a7979ca 884
629d9f78
BF
885[[showing-commits-unique-to-a-branch]]
886Showing commits unique to a given branch
887~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4a7979ca 888
629d9f78 889Suppose you would like to see all the commits reachable from the branch
1249d8ad 890head named `master` but not from any other head in your repository.
d19fbc3c 891
629d9f78 892We can list all the heads in this repository with
5162e697 893linkgit:git-show-ref[1]:
d19fbc3c 894
629d9f78
BF
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-------------------------------------------------
d19fbc3c 903
1249d8ad 904We can get just the branch-head names, and remove `master`, with
629d9f78
BF
905the 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 $( git show-ref --heads | cut -d' ' -f2 |
920 grep -v '^refs/heads/master' )
921-------------------------------------------------
922
923Obviously, endless variations are possible; for example, to see all
924commits reachable from some head but not from any tag in the repository:
925
926-------------------------------------------------
c78974f7 927$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )
629d9f78
BF
928-------------------------------------------------
929
9d83e382 930(See linkgit:gitrevisions[7] for explanations of commit-selecting
629d9f78
BF
931syntax such as `--not`.)
932
82c8bf28
BF
933[[making-a-release]]
934Creating a changelog and tarball for a software release
935~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
936
5162e697 937The linkgit:git-archive[1] command can create a tar or zip archive from
82c8bf28
BF
938any version of a project; for example:
939
940-------------------------------------------------
7ed1690c 941$ git archive -o latest.tar.gz --prefix=project/ HEAD
82c8bf28
BF
942-------------------------------------------------
943
7ed1690c
TK
944will 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
1249d8ad 949Versions of Git older than 1.7.7 don't know about the `tar.gz` format,
7ed1690c
TK
950you'll need to use gzip explicitly:
951
952-------------------------------------------------
953$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz
954-------------------------------------------------
82c8bf28
BF
955
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.
4a7979ca 984
e1ba4c32 985[[Finding-commits-With-given-Content]]
187b0d80 986Finding commits referencing a file with given content
d5821de2 987~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
187b0d80
BF
988
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-------------------------------------------------
477ff5b7 994$ git log --raw --abbrev=40 --pretty=oneline |
187b0d80
BF
995 grep -B 1 `git hash-object filename`
996-------------------------------------------------
997
998Figuring out why this works is left as an exercise to the (advanced)
5162e697
DM
999student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and
1000linkgit:git-hash-object[1] man pages may prove helpful.
187b0d80 1001
aa971cb9 1002[[Developing-With-git]]
2de9b711 1003Developing with Git
d19fbc3c
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1004===================
1005
e34caace 1006[[telling-git-your-name]]
2de9b711 1007Telling Git your name
d19fbc3c
BF
1008---------------------
1009
632cc3e6
TK
1010Before 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:
d19fbc3c
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1020
1021------------------------------------------------
d19fbc3c
BF
1022[user]
1023 name = Your Name Comes Here
1024 email = you@yourdomain.example.com
d19fbc3c
BF
1025------------------------------------------------
1026
632cc3e6
TK
1027See 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.
fc90c536 1030
d19fbc3c 1031
e34caace 1032[[creating-a-new-repository]]
d19fbc3c
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1033Creating a new repository
1034-------------------------
1035
1036Creating a new repository from scratch is very easy:
1037
1038-------------------------------------------------
1039$ mkdir project
1040$ cd project
f1d2b477 1041$ git init
d19fbc3c
BF
1042-------------------------------------------------
1043
1044If you have some initial content (say, a tarball):
1045
1046-------------------------------------------------
0ddd93b2 1047$ tar xzvf project.tar.gz
d19fbc3c 1048$ cd project
f1d2b477 1049$ git init
d19fbc3c
BF
1050$ git add . # include everything below ./ in the first commit:
1051$ git commit
1052-------------------------------------------------
1053
1054[[how-to-make-a-commit]]
ae25c67a 1055How to make a commit
d19fbc3c
BF
1056--------------------
1057
1058Creating a new commit takes three steps:
1059
1060 1. Making some changes to the working directory using your
1061 favorite editor.
2de9b711
TA
1062 2. Telling Git about your changes.
1063 3. Creating the commit using the content you told Git about
d19fbc3c
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1064 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
2de9b711 1068at step 3, Git maintains a snapshot of the tree's contents in a
d19fbc3c
BF
1069special staging area called "the index."
1070
01997b4a 1071At the beginning, the content of the index will be identical to
1249d8ad 1072that of the HEAD. The command `git diff --cached`, which shows
01997b4a
BF
1073the difference between the HEAD and the index, should therefore
1074produce no output at that point.
eb6ae7f4 1075
d19fbc3c
BF
1076Modifying the index is easy:
1077
d39765b1 1078To update the index with the contents of a new or modified file, use
d19fbc3c
BF
1079
1080-------------------------------------------------
1081$ git add path/to/file
1082-------------------------------------------------
1083
d39765b1 1084To remove a file from the index and from the working tree, use
d19fbc3c
BF
1085
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
1249d8ad 1105Note that `git add` always adds just the current contents of a file
d19fbc3c 1106to the index; further changes to the same file will be ignored unless
6127c086 1107you run `git add` on the file again.
d19fbc3c
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1108
1109When you're ready, just run
1110
1111-------------------------------------------------
1112$ git commit
1113-------------------------------------------------
1114
2de9b711 1115and Git will prompt you for a commit message and then create the new
3dff5379 1116commit. Check to make sure it looks like what you expected with
d19fbc3c
BF
1117
1118-------------------------------------------------
1119$ git show
1120-------------------------------------------------
1121
1122As a special shortcut,
a6080a0a 1123
d19fbc3c
BF
1124-------------------------------------------------
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
1130845b 1136 # would be committed if you ran "commit" now.
d19fbc3c
BF
1137$ git diff # difference between the index file and your
1138 # working directory; changes that would not
1139 # be included if you ran "commit" now.
c64415e2
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1140$ git diff HEAD # difference between HEAD and working tree; what
1141 # would be committed if you ran "commit -a" now.
d19fbc3c
BF
1142$ git status # a brief per-file summary of the above.
1143-------------------------------------------------
1144
5162e697 1145You can also use linkgit:git-gui[1] to create commits, view changes in
407c0c87
BF
1146the 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
e34caace 1150[[creating-good-commit-messages]]
ae25c67a 1151Creating good commit messages
d19fbc3c
BF
1152-----------------------------
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
52ffe995
JW
1157description. The text up to the first blank line in a commit
1158message is treated as the commit title, and that title is used
2de9b711 1159throughout Git. For example, linkgit:git-format-patch[1] turns a
52ffe995
JW
1160commit into email, and it uses the title on the Subject line and the
1161rest of the commit in the body.
1162
d19fbc3c 1163
2dc53617
JH
1164[[ignoring-files]]
1165Ignoring files
1166--------------
1167
2de9b711 1168A project will often generate files that you do 'not' want to track with Git.
2dc53617 1169This typically includes files generated by a build process or temporary
2de9b711 1170backup files made by your editor. Of course, 'not' tracking files with Git
6127c086 1171is just a matter of 'not' calling `git add` on them. But it quickly becomes
2dc53617 1172annoying to have these untracked files lying around; e.g. they make
dcb11263
CJ
1173`git add .` practically useless, and they keep showing up in the output of
1174`git status`.
2dc53617 1175
1249d8ad
TK
1176You 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:
2dc53617
JH
1179
1180-------------------------------------------------
1181# Lines starting with '#' are considered comments.
464a8a7a 1182# Ignore any file named foo.txt.
2dc53617
JH
1183foo.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
5162e697 1192See linkgit:gitignore[5] for a detailed explanation of the syntax. You can
464a8a7a
BF
1193also 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.
1199
1200If you wish the exclude patterns to affect only certain repositories
1201(instead of every repository for a given project), you may instead put
1249d8ad 1202them in a file in your repository named `.git/info/exclude`, or in any
da0005b8 1203file specified by the `core.excludesFile` configuration variable.
1249d8ad
TK
1204Some Git commands can also take exclude patterns directly on the
1205command line. See linkgit:gitignore[5] for the details.
2dc53617 1206
e34caace 1207[[how-to-merge]]
ae25c67a 1208How to merge
d19fbc3c
BF
1209------------
1210
1211You can rejoin two diverging branches of development using
5162e697 1212linkgit:git-merge[1]:
d19fbc3c
BF
1213
1214-------------------------------------------------
1215$ git merge branchname
1216-------------------------------------------------
1217
1249d8ad 1218merges the development in the branch `branchname` into the current
e63ec003
MM
1219branch.
1220
1249d8ad 1221A merge is made by combining the changes made in `branchname` and the
e63ec003
MM
1222changes 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
6a5d0b0a 1232If the changes are independent enough, Git will automatically complete
e63ec003
MM
1233the 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
d19fbc3c
BF
1236modified 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-------------------------------------------------
fabbd8f6
BF
1240$ git merge next
1241 100% (4/4) done
1242Auto-merged file.txt
d19fbc3c
BF
1243CONFLICT (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
2de9b711 1249with the contents and run Git commit, as you normally would when
d19fbc3c
BF
1250creating 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
d19fbc3c
BF
1256[[resolving-a-merge]]
1257Resolving a merge
1258-----------------
1259
2de9b711 1260When a merge isn't resolved automatically, Git leaves the index and
d19fbc3c
BF
1261the 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
5162e697 1265resolve the problem and update the index, linkgit:git-commit[1] will
ef561ac7 1266fail:
d19fbc3c
BF
1267
1268-------------------------------------------------
1269$ git commit
1270file.txt: needs merge
1271-------------------------------------------------
1272
5162e697 1273Also, linkgit:git-status[1] will list those files as "unmerged", and the
ef561ac7
BF
1274files 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
2de9b711 1296The above is all you need to know to resolve a simple merge. But Git
ef561ac7
BF
1297also provides more information to help resolve conflicts:
1298
e34caace 1299[[conflict-resolution]]
ef561ac7
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1300Getting conflict-resolution help during a merge
1301~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 1302
2de9b711 1303All of the changes that Git was able to merge automatically are
5162e697 1304already added to the index file, so linkgit:git-diff[1] shows only
ef561ac7 1305the conflicts. It uses an unusual syntax:
d19fbc3c
BF
1306
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
1130845b 1321Recall that the commit which will be committed after we resolve this
d19fbc3c
BF
1322conflict 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
ef561ac7
BF
1326During 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
4209752d
JH
1331$ git show :2:file.txt # the version from HEAD.
1332$ git show :3:file.txt # the version from MERGE_HEAD.
ef561ac7
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1333-------------------------------------------------
1334
4209752d
JH
1335When 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).
ef561ac7
BF
1340
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
1249d8ad 1343each line by a single `+` or `-`, it now uses two columns: the first
ef561ac7
BF
1344column 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
5162e697 1347of linkgit:git-diff-files[1] for a details of the format.)
ef561ac7
BF
1348
1349After resolving the conflict in the obvious way (but before updating the
1350index), the diff will look like:
d19fbc3c
BF
1351
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
ef561ac7
BF
1368Some 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
0cafe944 1380The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help
ef561ac7 1381for merges:
d19fbc3c
BF
1382
1383-------------------------------------------------
1384$ git log --merge
ef561ac7 1385$ gitk --merge
d19fbc3c
BF
1386-------------------------------------------------
1387
ef561ac7
BF
1388These will display all commits which exist only on HEAD or on
1389MERGE_HEAD, and which touch an unmerged file.
d19fbc3c 1390
5162e697 1391You may also use linkgit:git-mergetool[1], which lets you merge the
c7719fbe 1392unmerged files using external tools such as Emacs or kdiff3.
c64415e2 1393
ef561ac7 1394Each time you resolve the conflicts in a file and update the index:
d19fbc3c
BF
1395
1396-------------------------------------------------
1397$ git add file.txt
d19fbc3c
BF
1398-------------------------------------------------
1399
ef561ac7 1400the different stages of that file will be "collapsed", after which
6127c086 1401`git diff` will (by default) no longer show diffs for that file.
d19fbc3c
BF
1402
1403[[undoing-a-merge]]
ae25c67a 1404Undoing a merge
d19fbc3c
BF
1405---------------
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
1130845b 1414Or, if you've already committed the merge that you want to throw away,
d19fbc3c
BF
1415
1416-------------------------------------------------
1c73bb0e 1417$ git reset --hard ORIG_HEAD
d19fbc3c
BF
1418-------------------------------------------------
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
e34caace 1425[[fast-forwards]]
d19fbc3c
BF
1426Fast-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
b2af4829
XF
1434However, if the current branch is an ancestor of the other--so every commit
1435present in the current branch is already contained in the other branch--then Git
1436just performs a "fast-forward"; the head of the current branch is moved forward
1437to point at the head of the merged-in branch, without any new commits being
1438created.
d19fbc3c 1439
e34caace 1440[[fixing-mistakes]]
b684f830
BF
1441Fixing 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
1455 1. You can create a new commit that undoes whatever was done
93cbbd71 1456 by the old commit. This is the correct thing if your
b684f830
BF
1457 mistake has already been made public.
1458
1459 2. You can go back and modify the old commit. You should
1460 never do this if you have already made the history public;
2de9b711 1461 Git does not normally expect the "history" of a project to
b684f830
BF
1462 change, and cannot correctly perform repeated merges from
1463 a branch that has had its history changed.
1464
e34caace 1465[[reverting-a-commit]]
b684f830
BF
1466Fixing a mistake with a new commit
1467~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1468
1469Creating a new commit that reverts an earlier change is very easy;
5162e697 1470just pass the linkgit:git-revert[1] command a reference to the bad
b684f830
BF
1471commit; 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
2de9b711 1486In this case Git will attempt to undo the old change while leaving
b684f830
BF
1487intact 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
7cb192ea
BF
1492[[fixing-a-mistake-by-rewriting-history]]
1493Fixing a mistake by rewriting history
a3e1fa97 1494~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
b684f830
BF
1495
1496If the problematic commit is the most recent commit, and you have not
1497yet made that commit public, then you may just
6127c086 1498<<undoing-a-merge,destroy it using `git reset`>>.
b684f830
BF
1499
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
5162e697 1513been merged into another branch; use linkgit:git-revert[1] instead in
b684f830
BF
1514that case.
1515
7cb192ea 1516It is also possible to replace commits further back in the history, but
b684f830
BF
1517this is an advanced topic to be left for
1518<<cleaning-up-history,another chapter>>.
1519
e34caace 1520[[checkout-of-path]]
b684f830
BF
1521Checking 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
6127c086 1526linkgit:git-checkout[1]. We've used `git checkout` before to switch
b684f830
BF
1527branches, 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
5162e697 1539linkgit:git-show[1]:
b684f830
BF
1540
1541-------------------------------------------------
ed4eb0d8 1542$ git show HEAD^:path/to/file
b684f830
BF
1543-------------------------------------------------
1544
1545which will display the given version of the file.
1546
7a7cc594
JH
1547[[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
5162e697 1553before continuing. You can use linkgit:git-stash[1] to save the current
7a7cc594
JH
1554state 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------------------------------------------------
7a85f6ae 1559$ git stash save "work in progress for foo feature"
7a7cc594
JH
1560------------------------------------------------
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
7b8988e1 1572`git stash pop`:
7a7cc594
JH
1573
1574------------------------------------------------
7b8988e1 1575$ git stash pop
7a7cc594
JH
1576------------------------------------------------
1577
1578
e34caace 1579[[ensuring-good-performance]]
d19fbc3c
BF
1580Ensuring good performance
1581-------------------------
1582
2de9b711 1583On large repositories, Git depends on compression to keep the history
901fd180 1584information from taking up too much space on disk or in memory. Some
e1ebf212 1585Git commands may automatically run linkgit:git-gc[1], so you don't
901fd180
TK
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.
d19fbc3c 1589
e34caace
BF
1590
1591[[ensuring-reliability]]
11e016a3
BF
1592Ensuring reliability
1593--------------------
1594
e34caace 1595[[checking-for-corruption]]
11e016a3
BF
1596Checking the repository for corruption
1597~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1598
5162e697 1599The linkgit:git-fsck[1] command runs a number of self-consistency checks
1191ee18 1600on the repository, and reports on any problems. This may take some
c6a13b2c 1601time.
21dcb3b7
BF
1602
1603-------------------------------------------------
04e50e94 1604$ git fsck
21dcb3b7
BF
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
c6a13b2c
JH
1616You will see informational messages on dangling objects. They are objects
1617that still exist in the repository but are no longer referenced by any of
1249d8ad 1618your branches, and can (and will) be removed after a while with `gc`.
b4ab1980 1619You can run `git fsck --no-dangling` to suppress these messages, and still
c6a13b2c 1620view real errors.
1cdade2c 1621
e34caace 1622[[recovering-lost-changes]]
11e016a3
BF
1623Recovering lost changes
1624~~~~~~~~~~~~~~~~~~~~~~~
1625
e34caace 1626[[reflogs]]
559e4d7a
BF
1627Reflogs
1628^^^^^^^
1629
1249d8ad
TK
1630Say 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.
559e4d7a 1633
2de9b711 1634Fortunately, Git also keeps a log, called a "reflog", of all the
559e4d7a 1635previous values of each branch. So in this case you can still find the
a6080a0a 1636old history using, for example,
559e4d7a
BF
1637
1638-------------------------------------------------
1639$ git log master@{1}
1640-------------------------------------------------
1641
e502c2c3 1642This lists the commits reachable from the previous version of the
1249d8ad
TK
1643`master` branch head. This syntax can be used with any Git command
1644that accepts a commit, not just with `git log`. Some other examples:
559e4d7a
BF
1645
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
953f3d6f
BF
1651$ git log --walk-reflogs master # show reflog entries for master
1652-------------------------------------------------
1653
1654A separate reflog is kept for the HEAD, so
1655
1656-------------------------------------------------
1657$ git show HEAD@{"1 week ago"}
559e4d7a
BF
1658-------------------------------------------------
1659
953f3d6f
BF
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
559e4d7a 1664The reflogs are kept by default for 30 days, after which they may be
5162e697 1665pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn
559e4d7a 1666how to control this pruning, and see the "SPECIFYING REVISIONS"
9d83e382 1667section of linkgit:gitrevisions[7] for details.
559e4d7a 1668
2de9b711 1669Note that the reflog history is very different from normal Git history.
559e4d7a
BF
1670While 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
59723040 1674[[dangling-object-recovery]]
559e4d7a
BF
1675Examining dangling objects
1676^^^^^^^^^^^^^^^^^^^^^^^^^^
1677
59723040
BF
1678In 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
6127c086 1682commits in the dangling objects that `git fsck` reports. See
59723040 1683<<dangling-objects>> for the details.
559e4d7a
BF
1684
1685-------------------------------------------------
1686$ git fsck
1687dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1688dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1689dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1690...
1691-------------------------------------------------
1692
aacd404e 1693You can examine
559e4d7a
BF
1694one 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
79c96c57 1706and complex commit history that was dropped.)
559e4d7a
BF
1707
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------------------------------------------------
a6080a0a 1712$ git branch recovered-branch 7281251ddd
559e4d7a
BF
1713------------------------------------------------
1714
59723040
BF
1715Other types of dangling objects (blobs and trees) are also possible, and
1716dangling objects can arise in other situations.
1717
11e016a3 1718
e34caace 1719[[sharing-development]]
d19fbc3c 1720Sharing development with others
b684f830 1721===============================
d19fbc3c 1722
aa971cb9 1723[[getting-updates-With-git-pull]]
6127c086 1724Getting updates with git pull
b684f830 1725-----------------------------
d19fbc3c 1726
e63ec003 1727After you clone a repository and commit a few changes of your own, you
d19fbc3c
BF
1728may wish to check the original repository for updates and merge them
1729into your own work.
1730
aa971cb9 1731We have already seen <<Updating-a-repository-With-git-fetch,how to
0e615b25 1732keep remote-tracking branches up to date>> with linkgit:git-fetch[1],
d19fbc3c
BF
1733and 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
5162e697 1741However, the linkgit:git-pull[1] command provides a way to do this in
d19fbc3c
BF
1742one step:
1743
1744-------------------------------------------------
1745$ git pull origin master
1746-------------------------------------------------
1747
1249d8ad
TK
1748In 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
66a062a1 1750origin repository. So often you can
0eb4f7cd 1751accomplish the above with just a simple
d19fbc3c
BF
1752
1753-------------------------------------------------
1754$ git pull
1755-------------------------------------------------
1756
66a062a1
MM
1757This command will fetch changes from the remote branches to your
1758remote-tracking branches `origin/*`, and merge the default branch into
1759the current branch.
1760
29b9a66f
MM
1761More generally, a branch that is created from a remote-tracking branch
1762will pull
0eb4f7cd 1763by default from that branch. See the descriptions of the
1249d8ad 1764`branch.<name>.remote` and `branch.<name>.merge` options in
5162e697
DM
1765linkgit:git-config[1], and the discussion of the `--track` option in
1766linkgit:git-checkout[1], to learn how to control these defaults.
d19fbc3c 1767
1249d8ad 1768In addition to saving you keystrokes, `git pull` also helps you by
d19fbc3c
BF
1769producing 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
a75d7b54 1773<<fast-forwards,fast-forward>>; instead, your branch will just be
79c96c57 1774updated to point to the latest commit from the upstream branch.)
d19fbc3c 1775
1249d8ad 1776The `git pull` command can also be given `.` as the "remote" repository,
1191ee18 1777in which case it just merges in a branch from the current repository; so
4c63ff45
BF
1778the commands
1779
1780-------------------------------------------------
1781$ git pull . branch
1782$ git merge branch
1783-------------------------------------------------
1784
a7bdee11 1785are roughly equivalent.
4c63ff45 1786
e34caace 1787[[submitting-patches]]
d19fbc3c 1788Submitting patches to a project
b684f830 1789-------------------------------
d19fbc3c
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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
5162e697 1794First, use linkgit:git-format-patch[1]; for example:
d19fbc3c
BF
1795
1796-------------------------------------------------
eb6ae7f4 1797$ git format-patch origin
d19fbc3c
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1798-------------------------------------------------
1799
1800will produce a numbered series of files in the current directory, one
1249d8ad 1801for each patch in the current branch but not in `origin/HEAD`.
d19fbc3c 1802
d84cef18
PO
1803`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
d19fbc3c
BF
1810You 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
5162e697 1812use the linkgit:git-send-email[1] script to automate the process.
3c735e07
JM
1813Consult the mailing list for your project first to determine
1814their requirements for submitting patches.
d19fbc3c 1815
e34caace 1816[[importing-patches]]
d19fbc3c 1817Importing patches to a project
b684f830 1818------------------------------
d19fbc3c 1819
5162e697 1820Git also provides a tool called linkgit:git-am[1] (am stands for
d19fbc3c
BF
1821"apply mailbox"), for importing such an emailed series of patches.
1822Just save all of the patch-containing messages, in order, into a
1249d8ad 1823single mailbox file, say `patches.mbox`, then run
d19fbc3c
BF
1824
1825-------------------------------------------------
eb6ae7f4 1826$ git am -3 patches.mbox
d19fbc3c
BF
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
1249d8ad 1831"<<resolving-a-merge,Resolving a merge>>". (The `-3` option tells
2de9b711 1832Git to perform a merge; if you would prefer it just to abort and
01997b4a
BF
1833leave 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
d19fbc3c
BF
1837
1838-------------------------------------------------
8ceb6fbd 1839$ git am --continue
d19fbc3c
BF
1840-------------------------------------------------
1841
2de9b711 1842and Git will create the commit for you and continue applying the
d19fbc3c
BF
1843remaining 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
eda69449 1849[[public-repositories]]
2de9b711 1850Public Git repositories
eda69449 1851-----------------------
d19fbc3c 1852
6e30fb0c
DK
1853Another way to submit changes to a project is to tell the maintainer
1854of that project to pull the changes from your repository using
aa971cb9 1855linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull,
6127c086 1856Getting updates with `git pull`>>" we described this as a way to get
6e30fb0c
DK
1857updates from the "main" repository, but it works just as well in the
1858other direction.
d19fbc3c 1859
eda69449
BF
1860If you and the maintainer both have accounts on the same machine, then
1861you can just pull changes from each other's repositories directly;
11d51533 1862commands that accept repository URLs as arguments will also accept a
eda69449 1863local directory name:
d19fbc3c
BF
1864
1865-------------------------------------------------
1866$ git clone /path/to/repository
1867$ git pull /path/to/other/repository
1868-------------------------------------------------
1869
c9016158 1870or an ssh URL:
11d51533
BF
1871
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
eda69449
BF
1879However, 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.
d19fbc3c
BF
1883
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
a6080a0a 1893 ^ |
d19fbc3c
BF
1894 | |
1895 | you pull | they pull
1896 | |
1897 | |
1898 | they push V
1899 their public repo <------------------- their repo
1900
11d51533
BF
1901We explain how to do this in the following sections.
1902
eda69449
BF
1903[[setting-up-a-public-repository]]
1904Setting up a public repository
1905~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1906
1249d8ad 1907Assume your personal repository is in the directory `~/proj`. We
6127c086 1908first create a new clone of the repository and tell `git daemon` that it
eda69449 1909is meant to be public:
d19fbc3c
BF
1910
1911-------------------------------------------------
52c80037 1912$ git clone --bare ~/proj proj.git
eda69449 1913$ touch proj.git/git-daemon-export-ok
d19fbc3c
BF
1914-------------------------------------------------
1915
52c80037 1916The resulting directory proj.git contains a "bare" git repository--it is
1249d8ad 1917just the contents of the `.git` directory, without any files checked out
eda69449 1918around it.
d19fbc3c 1919
1249d8ad 1920Next, copy `proj.git` to the server where you plan to host the
d19fbc3c
BF
1921public repository. You can use scp, rsync, or whatever is most
1922convenient.
1923
eda69449 1924[[exporting-via-git]]
2de9b711 1925Exporting a Git repository via the Git protocol
eda69449
BF
1926~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1927
1928This is the preferred method.
1929
1930If someone else administers the server, they should tell you what
1249d8ad
TK
1931directory to put the repository in, and what `git://` URL it will
1932appear at. You can then skip to the section
d19fbc3c
BF
1933"<<pushing-changes-to-a-public-repository,Pushing changes to a public
1934repository>>", below.
1935
5162e697 1936Otherwise, all you need to do is start linkgit:git-daemon[1]; it will
eda69449 1937listen on port 9418. By default, it will allow access to any directory
2de9b711 1938that looks like a Git directory and contains the magic file
6127c086 1939git-daemon-export-ok. Passing some directory paths as `git daemon`
eda69449
BF
1940arguments will further restrict the exports to those paths.
1941
6127c086 1942You can also run `git daemon` as an inetd service; see the
5162e697 1943linkgit:git-daemon[1] man page for details. (See especially the
eda69449 1944examples section.)
d19fbc3c
BF
1945
1946[[exporting-via-http]]
de3f2c7b 1947Exporting a git repository via HTTP
eda69449 1948~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 1949
2de9b711 1950The Git protocol gives better performance and reliability, but on a
de3f2c7b 1951host with a web server set up, HTTP exports may be simpler to set up.
d19fbc3c 1952
2de9b711 1953All you need to do is place the newly created bare Git repository in
d19fbc3c
BF
1954a 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
c64415e2 1960$ git --bare update-server-info
7dce9918 1961$ mv hooks/post-update.sample hooks/post-update
d19fbc3c
BF
1962-------------------------------------------------
1963
1964(For an explanation of the last two lines, see
6998e4db 1965linkgit:git-update-server-info[1] and linkgit:githooks[5].)
d19fbc3c 1966
1249d8ad 1967Advertise the URL of `proj.git`. Anybody else should then be able to
c9016158 1968clone or pull from that URL, for example with a command line like:
d19fbc3c
BF
1969
1970-------------------------------------------------
1971$ git clone http://yourserver.com/~you/proj.git
1972-------------------------------------------------
1973
1974(See also
d5ff3b4b 1975link:howto/setup-git-server-over-http.html[setup-git-server-over-http]
d19fbc3c 1976for a slightly more sophisticated setup using WebDAV which also
de3f2c7b 1977allows pushing over HTTP.)
d19fbc3c 1978
d19fbc3c
BF
1979[[pushing-changes-to-a-public-repository]]
1980Pushing changes to a public repository
eda69449 1981~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 1982
eda69449 1983Note that the two techniques outlined above (exporting via
d19fbc3c
BF
1984<<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
5162e697 1989The simplest way to do this is using linkgit:git-push[1] and ssh; to
1249d8ad
TK
1990update the remote branch named `master` with the latest state of your
1991branch named `master`, run
d19fbc3c
BF
1992
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
6127c086 2003As with `git fetch`, `git push` will complain if this does not result in a
a75d7b54 2004<<fast-forwards,fast-forward>>; see the following section for details on
81eb417a 2005handling this case.
d19fbc3c 2006
1249d8ad 2007Note that the target of a `push` is normally a
11d51533 2008<<def_bare_repository,bare>> repository. You can also push to a
d9be2485
TK
2009repository that has a checked-out working tree, but a push to update the
2010currently checked-out branch is denied by default to prevent confusion.
50995edd 2011See the description of the receive.denyCurrentBranch option
d9be2485 2012in linkgit:git-config[1] for details.
11d51533 2013
6127c086 2014As with `git fetch`, you may also set up configuration options to
e9b49083
TK
2015save typing; so, for example:
2016
2017-------------------------------------------------
2018$ git remote add public-repo ssh://yourserver.com/~you/proj.git
2019-------------------------------------------------
2020
2021adds the following to `.git/config`:
d19fbc3c
BF
2022
2023-------------------------------------------------
d19fbc3c 2024[remote "public-repo"]
e9b49083
TK
2025 url = yourserver.com:proj.git
2026 fetch = +refs/heads/*:refs/remotes/example/*
d19fbc3c
BF
2027-------------------------------------------------
2028
e9b49083 2029which lets you do the same push with just
d19fbc3c
BF
2030
2031-------------------------------------------------
2032$ git push public-repo master
2033-------------------------------------------------
2034
1249d8ad
TK
2035See the explanations of the `remote.<name>.url`,
2036`branch.<name>.remote`, and `remote.<name>.push` options in
2037linkgit:git-config[1] for details.
d19fbc3c 2038
81eb417a
BF
2039[[forcing-push]]
2040What to do when a push fails
2041~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2042
a75d7b54 2043If a push would not result in a <<fast-forwards,fast-forward>> of the
81eb417a
BF
2044remote branch, then it will fail with an error like:
2045
2046-------------------------------------------------
3c82eec8
2047 ! [rejected] master -> master (non-fast-forward)
2048error: failed to push some refs to '...'
2049hint: Updates were rejected because the tip of your current branch is behind
2050hint: its remote counterpart. Integrate the remote changes (e.g.
2051hint: 'git pull ...') before pushing again.
2052hint: See the 'Note about fast-forwards' in 'git push --help' for details.
81eb417a
BF
2053-------------------------------------------------
2054
2055This can happen, for example, if you:
2056
6127c086
FC
2057 - use `git reset --hard` to remove already-published commits, or
2058 - use `git commit --amend` to replace already-published commits
7cb192ea 2059 (as in <<fixing-a-mistake-by-rewriting-history>>), or
6127c086 2060 - use `git rebase` to rebase any already-published commits (as
81eb417a
BF
2061 in <<using-git-rebase>>).
2062
6127c086 2063You may force `git push` to perform the update anyway by preceding the
81eb417a
BF
2064branch name with a plus sign:
2065
2066-------------------------------------------------
2067$ git push ssh://yourserver.com/~you/proj.git +master
2068-------------------------------------------------
2069
d1471e06
TK
2070Note the addition of the `+` sign. Alternatively, you can use the
2071`-f` flag to force the remote update, as in:
2072
2073-------------------------------------------------
2074$ git push -f ssh://yourserver.com/~you/proj.git master
2075-------------------------------------------------
2076
81eb417a 2077Normally whenever a branch head in a public repository is modified, it
9e5d87d4 2078is modified to point to a descendant of the commit that it pointed to
81eb417a 2079before. By forcing a push in this situation, you break that convention.
aa971cb9 2080(See <<problems-With-rewriting-history>>.)
81eb417a
BF
2081
2082Nevertheless, this is a common practice for people that need a simple
2083way to publish a work-in-progress patch series, and it is an acceptable
2084compromise as long as you warn other developers that this is how you
2085intend to manage the branch.
2086
2087It's also possible for a push to fail in this way when other people have
2088the right to push to the same repository. In that case, the correct
843c81dc
EH
2089solution is to retry the push after first updating your work: either by a
2090pull, or by a fetch followed by a rebase; see the
81eb417a 2091<<setting-up-a-shared-repository,next section>> and
6998e4db 2092linkgit:gitcvs-migration[7] for more.
81eb417a 2093
e34caace 2094[[setting-up-a-shared-repository]]
d19fbc3c 2095Setting up a shared repository
eda69449 2096~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c
BF
2097
2098Another way to collaborate is by using a model similar to that
2099commonly used in CVS, where several developers with special rights
2100all push to and pull from a single shared repository. See
6998e4db 2101linkgit:gitcvs-migration[7] for instructions on how to
d19fbc3c
BF
2102set this up.
2103
2de9b711 2104However, while there is nothing wrong with Git's support for shared
8fae2225 2105repositories, this mode of operation is not generally recommended,
2de9b711 2106simply because the mode of collaboration that Git supports--by
8fae2225
BF
2107exchanging patches and pulling from public repositories--has so many
2108advantages over the central shared repository:
2109
2110 - Git's ability to quickly import and merge patches allows a
2111 single maintainer to process incoming changes even at very
6127c086 2112 high rates. And when that becomes too much, `git pull` provides
8fae2225
BF
2113 an easy way for that maintainer to delegate this job to other
2114 maintainers while still allowing optional review of incoming
2115 changes.
2116 - Since every developer's repository has the same complete copy
2117 of the project history, no repository is special, and it is
2118 trivial for another developer to take over maintenance of a
2119 project, either by mutual agreement, or because a maintainer
2120 becomes unresponsive or difficult to work with.
2121 - The lack of a central group of "committers" means there is
2122 less need for formal decisions about who is "in" and who is
2123 "out".
2124
e34caace 2125[[setting-up-gitweb]]
eda69449
BF
2126Allowing web browsing of a repository
2127~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 2128
a8cd1402 2129The gitweb cgi script provides users an easy way to browse your
99487cf2
SS
2130project's revisions, file contents and logs without having to install
2131Git. Features like RSS/Atom feeds and blame/annotation details may
2132optionally be enabled.
2133
2134The linkgit:git-instaweb[1] command provides a simple way to start
2135browsing the repository using gitweb. The default server when using
2136instaweb is lighttpd.
2137
2138See the file gitweb/INSTALL in the Git source tree and
d285ab0a 2139linkgit:gitweb[1] for instructions on details setting up a permanent
99487cf2 2140installation with a CGI or Perl capable server.
d19fbc3c 2141
9cfde9ee
SS
2142[[how-to-get-a-git-repository-with-minimal-history]]
2143How to get a Git repository with minimal history
2144------------------------------------------------
2145
2146A <<def_shallow_clone,shallow clone>>, with its truncated
2147history, is useful when one is interested only in recent history
2148of a project and getting full history from the upstream is
2149expensive.
2150
2151A <<def_shallow_clone,shallow clone>> is created by specifying
2152the linkgit:git-clone[1] `--depth` switch. The depth can later be
2153changed with the linkgit:git-fetch[1] `--depth` switch, or full
2154history restored with `--unshallow`.
2155
2156Merging inside a <<def_shallow_clone,shallow clone>> will work as long
2157as a merge base is in the recent history.
2158Otherwise, it will be like merging unrelated histories and may
2159have to result in huge conflicts. This limitation may make such
2160a repository unsuitable to be used in merge based workflows.
d19fbc3c 2161
e34caace 2162[[sharing-development-examples]]
b684f830
BF
2163Examples
2164--------
d19fbc3c 2165
9e2163ea
BF
2166[[maintaining-topic-branches]]
2167Maintaining topic branches for a Linux subsystem maintainer
2168~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2169
2de9b711 2170This describes how Tony Luck uses Git in his role as maintainer of the
9e2163ea
BF
2171IA64 architecture for the Linux kernel.
2172
2173He uses two public branches:
2174
2175 - A "test" tree into which patches are initially placed so that they
2176 can get some exposure when integrated with other ongoing development.
2177 This tree is available to Andrew for pulling into -mm whenever he
2178 wants.
2179
2180 - A "release" tree into which tested patches are moved for final sanity
2181 checking, and as a vehicle to send them upstream to Linus (by sending
2182 him a "please pull" request.)
2183
2184He also uses a set of temporary branches ("topic branches"), each
2185containing a logical grouping of patches.
2186
2187To set this up, first create your work tree by cloning Linus's public
2188tree:
2189
2190-------------------------------------------------
283efb01 2191$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work
9e2163ea
BF
2192$ cd work
2193-------------------------------------------------
2194
29b9a66f 2195Linus's tree will be stored in the remote-tracking branch named origin/master,
5162e697
DM
2196and can be updated using linkgit:git-fetch[1]; you can track other
2197public trees using linkgit:git-remote[1] to set up a "remote" and
2198linkgit:git-fetch[1] to keep them up-to-date; see
6e30fb0c 2199<<repositories-and-branches>>.
9e2163ea
BF
2200
2201Now create the branches in which you are going to work; these start out
2202at the current tip of origin/master branch, and should be set up (using
1249d8ad 2203the `--track` option to linkgit:git-branch[1]) to merge changes in from
9e2163ea
BF
2204Linus by default.
2205
2206-------------------------------------------------
2207$ git branch --track test origin/master
2208$ git branch --track release origin/master
2209-------------------------------------------------
2210
5162e697 2211These can be easily kept up to date using linkgit:git-pull[1].
9e2163ea
BF
2212
2213-------------------------------------------------
2214$ git checkout test && git pull
2215$ git checkout release && git pull
2216-------------------------------------------------
2217
2218Important note! If you have any local changes in these branches, then
2219this merge will create a commit object in the history (with no local
2de9b711 2220changes Git will simply do a "fast-forward" merge). Many people dislike
9e2163ea 2221the "noise" that this creates in the Linux history, so you should avoid
1249d8ad 2222doing this capriciously in the `release` branch, as these noisy commits
9e2163ea
BF
2223will become part of the permanent history when you ask Linus to pull
2224from the release branch.
2225
5162e697 2226A few configuration variables (see linkgit:git-config[1]) can
9e2163ea
BF
2227make it easy to push both branches to your public tree. (See
2228<<setting-up-a-public-repository>>.)
2229
2230-------------------------------------------------
2231$ cat >> .git/config <<EOF
2232[remote "mytree"]
283efb01 2233 url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git
9e2163ea
BF
2234 push = release
2235 push = test
2236EOF
2237-------------------------------------------------
2238
2239Then you can push both the test and release trees using
5162e697 2240linkgit:git-push[1]:
9e2163ea
BF
2241
2242-------------------------------------------------
2243$ git push mytree
2244-------------------------------------------------
2245
2246or push just one of the test and release branches using:
2247
2248-------------------------------------------------
2249$ git push mytree test
2250-------------------------------------------------
2251
2252or
2253
2254-------------------------------------------------
2255$ git push mytree release
2256-------------------------------------------------
2257
2258Now to apply some patches from the community. Think of a short
2259snappy name for a branch to hold this patch (or related group of
352953a5
TL
2260patches), and create a new branch from a recent stable tag of
2261Linus's branch. Picking a stable base for your branch will:
22621) help you: by avoiding inclusion of unrelated and perhaps lightly
2263tested changes
1249d8ad 22642) help future bug hunters that use `git bisect` to find problems
9e2163ea
BF
2265
2266-------------------------------------------------
352953a5 2267$ git checkout -b speed-up-spinlocks v2.6.35
9e2163ea
BF
2268-------------------------------------------------
2269
2270Now you apply the patch(es), run some tests, and commit the change(s). If
2271the patch is a multi-part series, then you should apply each as a separate
2272commit to this branch.
2273
2274-------------------------------------------------
2275$ ... patch ... test ... commit [ ... patch ... test ... commit ]*
2276-------------------------------------------------
2277
a7bdee11 2278When you are happy with the state of this change, you can merge it into the
9e2163ea
BF
2279"test" branch in preparation to make it public:
2280
2281-------------------------------------------------
a7bdee11 2282$ git checkout test && git merge speed-up-spinlocks
9e2163ea
BF
2283-------------------------------------------------
2284
2285It is unlikely that you would have any conflicts here ... but you might if you
2286spent a while on this step and had also pulled new versions from upstream.
2287
3c735e07 2288Sometime later when enough time has passed and testing done, you can pull the
1249d8ad 2289same branch into the `release` tree ready to go upstream. This is where you
9e2163ea 2290see the value of keeping each patch (or patch series) in its own branch. It
1249d8ad 2291means that the patches can be moved into the `release` tree in any order.
9e2163ea
BF
2292
2293-------------------------------------------------
a7bdee11 2294$ git checkout release && git merge speed-up-spinlocks
9e2163ea
BF
2295-------------------------------------------------
2296
2297After a while, you will have a number of branches, and despite the
2298well chosen names you picked for each of them, you may forget what
2299they are for, or what status they are in. To get a reminder of what
2300changes are in a specific branch, use:
2301
2302-------------------------------------------------
467c0197 2303$ git log linux..branchname | git shortlog
9e2163ea
BF
2304-------------------------------------------------
2305
06ada152 2306To see whether it has already been merged into the test or release branches,
9e2163ea
BF
2307use:
2308
2309-------------------------------------------------
2310$ git log test..branchname
2311-------------------------------------------------
2312
2313or
2314
2315-------------------------------------------------
2316$ git log release..branchname
2317-------------------------------------------------
2318
06ada152 2319(If this branch has not yet been merged, you will see some log entries.
9e2163ea
BF
2320If it has been merged, then there will be no output.)
2321
2322Once a patch completes the great cycle (moving from test to release,
2323then pulled by Linus, and finally coming back into your local
1249d8ad 2324`origin/master` branch), the branch for this change is no longer needed.
9e2163ea
BF
2325You detect this when the output from:
2326
2327-------------------------------------------------
2328$ git log origin..branchname
2329-------------------------------------------------
2330
2331is empty. At this point the branch can be deleted:
2332
2333-------------------------------------------------
2334$ git branch -d branchname
2335-------------------------------------------------
2336
2337Some changes are so trivial that it is not necessary to create a separate
2338branch and then merge into each of the test and release branches. For
1249d8ad
TK
2339these changes, just apply directly to the `release` branch, and then
2340merge that into the `test` branch.
9e2163ea 2341
ae6ef554
TK
2342After pushing your work to `mytree`, you can use
2343linkgit:git-request-pull[1] to prepare a "please pull" request message
2344to send to Linus:
9e2163ea
BF
2345
2346-------------------------------------------------
ae6ef554
TK
2347$ git push mytree
2348$ git request-pull origin mytree release
9e2163ea
BF
2349-------------------------------------------------
2350
2351Here are some of the scripts that simplify all this even further.
2352
2353-------------------------------------------------
2354==== update script ====
48a8c26c 2355# Update a branch in my Git tree. If the branch to be updated
9e2163ea
BF
2356# is origin, then pull from kernel.org. Otherwise merge
2357# origin/master branch into test|release branch
2358
2359case "$1" in
2360test|release)
2361 git checkout $1 && git pull . origin
2362 ;;
2363origin)
fc74ecc1 2364 before=$(git rev-parse refs/remotes/origin/master)
9e2163ea 2365 git fetch origin
fc74ecc1 2366 after=$(git rev-parse refs/remotes/origin/master)
9e2163ea
BF
2367 if [ $before != $after ]
2368 then
2369 git log $before..$after | git shortlog
2370 fi
2371 ;;
2372*)
1a2ba8b9 2373 echo "usage: $0 origin|test|release" 1>&2
9e2163ea
BF
2374 exit 1
2375 ;;
2376esac
2377-------------------------------------------------
2378
2379-------------------------------------------------
2380==== merge script ====
2381# Merge a branch into either the test or release branch
2382
2383pname=$0
2384
2385usage()
2386{
1a2ba8b9 2387 echo "usage: $pname branch test|release" 1>&2
9e2163ea
BF
2388 exit 1
2389}
2390
fc74ecc1 2391git show-ref -q --verify -- refs/heads/"$1" || {
9e2163ea
BF
2392 echo "Can't see branch <$1>" 1>&2
2393 usage
fc74ecc1 2394}
9e2163ea
BF
2395
2396case "$2" in
2397test|release)
2398 if [ $(git log $2..$1 | wc -c) -eq 0 ]
2399 then
2400 echo $1 already merged into $2 1>&2
2401 exit 1
2402 fi
2403 git checkout $2 && git pull . $1
2404 ;;
2405*)
2406 usage
2407 ;;
2408esac
2409-------------------------------------------------
2410
2411-------------------------------------------------
2412==== status script ====
48a8c26c 2413# report on status of my ia64 Git tree
9e2163ea
BF
2414
2415gb=$(tput setab 2)
2416rb=$(tput setab 1)
2417restore=$(tput setab 9)
2418
2419if [ `git rev-list test..release | wc -c` -gt 0 ]
2420then
2421 echo $rb Warning: commits in release that are not in test $restore
2422 git log test..release
2423fi
2424
fc74ecc1 2425for branch in `git show-ref --heads | sed 's|^.*/||'`
9e2163ea
BF
2426do
2427 if [ $branch = test -o $branch = release ]
2428 then
2429 continue
2430 fi
2431
2432 echo -n $gb ======= $branch ====== $restore " "
2433 status=
2434 for ref in test release origin/master
2435 do
2436 if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
2437 then
2438 status=$status${ref:0:1}
2439 fi
2440 done
2441 case $status in
2442 trl)
2443 echo $rb Need to pull into test $restore
2444 ;;
2445 rl)
2446 echo "In test"
2447 ;;
2448 l)
2449 echo "Waiting for linus"
2450 ;;
2451 "")
2452 echo $rb All done $restore
2453 ;;
2454 *)
2455 echo $rb "<$status>" $restore
2456 ;;
2457 esac
2458 git log origin/master..$branch | git shortlog
2459done
2460-------------------------------------------------
d19fbc3c 2461
d19fbc3c 2462
d19fbc3c 2463[[cleaning-up-history]]
4c63ff45
BF
2464Rewriting history and maintaining patch series
2465==============================================
2466
2467Normally commits are only added to a project, never taken away or
2468replaced. Git is designed with this assumption, and violating it will
2de9b711 2469cause Git's merge machinery (for example) to do the wrong thing.
4c63ff45
BF
2470
2471However, there is a situation in which it can be useful to violate this
2472assumption.
2473
e34caace 2474[[patch-series]]
4c63ff45
BF
2475Creating the perfect patch series
2476---------------------------------
2477
2478Suppose you are a contributor to a large project, and you want to add a
2479complicated feature, and to present it to the other developers in a way
2480that makes it easy for them to read your changes, verify that they are
2481correct, and understand why you made each change.
2482
b181d57f 2483If you present all of your changes as a single patch (or commit), they
79c96c57 2484may find that it is too much to digest all at once.
4c63ff45
BF
2485
2486If you present them with the entire history of your work, complete with
2487mistakes, corrections, and dead ends, they may be overwhelmed.
2488
2489So the ideal is usually to produce a series of patches such that:
2490
2491 1. Each patch can be applied in order.
2492
2493 2. Each patch includes a single logical change, together with a
2494 message explaining the change.
2495
2496 3. No patch introduces a regression: after applying any initial
2497 part of the series, the resulting project still compiles and
2498 works, and has no bugs that it didn't have before.
2499
2500 4. The complete series produces the same end result as your own
2501 (probably much messier!) development process did.
2502
b181d57f
BF
2503We will introduce some tools that can help you do this, explain how to
2504use them, and then explain some of the problems that can arise because
2505you are rewriting history.
4c63ff45 2506
e34caace 2507[[using-git-rebase]]
6127c086 2508Keeping a patch series up to date using git rebase
4c63ff45
BF
2509--------------------------------------------------
2510
1249d8ad
TK
2511Suppose that you create a branch `mywork` on a remote-tracking branch
2512`origin`, and create some commits on top of it:
4c63ff45
BF
2513
2514-------------------------------------------------
2515$ git checkout -b mywork origin
2516$ vi file.txt
2517$ git commit
2518$ vi otherfile.txt
2519$ git commit
2520...
2521-------------------------------------------------
2522
2523You have performed no merges into mywork, so it is just a simple linear
1249d8ad 2524sequence of patches on top of `origin`:
4c63ff45 2525
1dc71a91 2526................................................
fa8347b8 2527 o--o--O <-- origin
4c63ff45 2528 \
fa8347b8 2529 a--b--c <-- mywork
1dc71a91 2530................................................
4c63ff45
BF
2531
2532Some more interesting work has been done in the upstream project, and
1249d8ad 2533`origin` has advanced:
4c63ff45 2534
1dc71a91 2535................................................
4c63ff45
BF
2536 o--o--O--o--o--o <-- origin
2537 \
2538 a--b--c <-- mywork
1dc71a91 2539................................................
4c63ff45 2540
1249d8ad 2541At this point, you could use `pull` to merge your changes back in;
4c63ff45
BF
2542the result would create a new merge commit, like this:
2543
1dc71a91 2544................................................
4c63ff45
BF
2545 o--o--O--o--o--o <-- origin
2546 \ \
2547 a--b--c--m <-- mywork
1dc71a91 2548................................................
a6080a0a 2549
4c63ff45
BF
2550However, if you prefer to keep the history in mywork a simple series of
2551commits without any merges, you may instead choose to use
5162e697 2552linkgit:git-rebase[1]:
4c63ff45
BF
2553
2554-------------------------------------------------
2555$ git checkout mywork
2556$ git rebase origin
2557-------------------------------------------------
2558
b181d57f 2559This will remove each of your commits from mywork, temporarily saving
1249d8ad 2560them as patches (in a directory named `.git/rebase-apply`), update mywork to
b181d57f
BF
2561point at the latest version of origin, then apply each of the saved
2562patches to the new mywork. The result will look like:
4c63ff45
BF
2563
2564
1dc71a91 2565................................................
4c63ff45
BF
2566 o--o--O--o--o--o <-- origin
2567 \
2568 a'--b'--c' <-- mywork
1dc71a91 2569................................................
4c63ff45 2570
b181d57f 2571In the process, it may discover conflicts. In that case it will stop
6127c086 2572and allow you to fix the conflicts; after fixing conflicts, use `git add`
7a7d4ef6 2573to update the index with those contents, and then, instead of
6127c086 2574running `git commit`, just run
4c63ff45
BF
2575
2576-------------------------------------------------
2577$ git rebase --continue
2578-------------------------------------------------
2579
2de9b711 2580and Git will continue applying the rest of the patches.
4c63ff45 2581
b6cbca38 2582At any point you may use the `--abort` option to abort this process and
4c63ff45
BF
2583return mywork to the state it had before you started the rebase:
2584
2585-------------------------------------------------
2586$ git rebase --abort
2587-------------------------------------------------
2588
6c26bf4d
TK
2589If you need to reorder or edit a number of commits in a branch, it may
2590be easier to use `git rebase -i`, which allows you to reorder and
2591squash commits, as well as marking them for individual editing during
2592the rebase. See <<interactive-rebase>> for details, and
2593<<reordering-patch-series>> for alternatives.
2594
7cb192ea
BF
2595[[rewriting-one-commit]]
2596Rewriting a single commit
365aa199
BF
2597-------------------------
2598
7cb192ea 2599We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the
365aa199
BF
2600most recent commit using
2601
2602-------------------------------------------------
2603$ git commit --amend
2604-------------------------------------------------
2605
2606which will replace the old commit by a new commit incorporating your
2607changes, giving you a chance to edit the old commit message first.
6c26bf4d
TK
2608This is useful for fixing typos in your last commit, or for adjusting
2609the patch contents of a poorly staged commit.
365aa199 2610
6c26bf4d
TK
2611If you need to amend commits from deeper in your history, you can
2612use <<interactive-rebase,interactive rebase's `edit` instruction>>.
365aa199 2613
6c26bf4d
TK
2614[[reordering-patch-series]]
2615Reordering or selecting from a patch series
2616-------------------------------------------
365aa199 2617
6c26bf4d
TK
2618Sometimes you want to edit a commit deeper in your history. One
2619approach is to use `git format-patch` to create a series of patches
2620and then reset the state to before the patches:
365aa199
BF
2621
2622-------------------------------------------------
6c26bf4d
TK
2623$ git format-patch origin
2624$ git reset --hard origin
365aa199
BF
2625-------------------------------------------------
2626
6c26bf4d
TK
2627Then modify, reorder, or eliminate patches as needed before applying
2628them again with linkgit:git-am[1]:
365aa199
BF
2629
2630-------------------------------------------------
6c26bf4d 2631$ git am *.patch
365aa199
BF
2632-------------------------------------------------
2633
6c26bf4d
TK
2634[[interactive-rebase]]
2635Using interactive rebases
2636-------------------------
365aa199 2637
6c26bf4d
TK
2638You can also edit a patch series with an interactive rebase. This is
2639the same as <<reordering-patch-series,reordering a patch series using
2640`format-patch`>>, so use whichever interface you like best.
4c63ff45 2641
6c26bf4d
TK
2642Rebase your current HEAD on the last commit you want to retain as-is.
2643For example, if you want to reorder the last 5 commits, use:
b181d57f
BF
2644
2645-------------------------------------------------
6c26bf4d 2646$ git rebase -i HEAD~5
b181d57f
BF
2647-------------------------------------------------
2648
6c26bf4d
TK
2649This will open your editor with a list of steps to be taken to perform
2650your rebase.
4c63ff45 2651
b181d57f 2652-------------------------------------------------
6c26bf4d
TK
2653pick deadbee The oneline of this commit
2654pick fa1afe1 The oneline of the next commit
2655...
4c63ff45 2656
6c26bf4d
TK
2657# Rebase c0ffeee..deadbee onto c0ffeee
2658#
2659# Commands:
2660# p, pick = use commit
2661# r, reword = use commit, but edit the commit message
2662# e, edit = use commit, but stop for amending
2663# s, squash = use commit, but meld into previous commit
2664# f, fixup = like "squash", but discard this commit's log message
2665# x, exec = run command (the rest of the line) using shell
2666#
2667# These lines can be re-ordered; they are executed from top to bottom.
2668#
2669# If you remove a line here THAT COMMIT WILL BE LOST.
2670#
2671# However, if you remove everything, the rebase will be aborted.
2672#
2673# Note that empty commits are commented out
2674-------------------------------------------------
2675
2676As explained in the comments, you can reorder commits, squash them
2677together, edit commit messages, etc. by editing the list. Once you
2678are satisfied, save the list and close your editor, and the rebase
2679will begin.
2680
2681The rebase will stop where `pick` has been replaced with `edit` or
2682when a step in the list fails to mechanically resolve conflicts and
2683needs your help. When you are done editing and/or resolving conflicts
2684you can continue with `git rebase --continue`. If you decide that
2685things are getting too hairy, you can always bail out with `git rebase
2686--abort`. Even after the rebase is complete, you can still recover
2687the original branch by using the <<reflogs,reflog>>.
2688
2689For a more detailed discussion of the procedure and additional tips,
2690see the "INTERACTIVE MODE" section of linkgit:git-rebase[1].
4c63ff45 2691
e34caace 2692[[patch-series-tools]]
4c63ff45
BF
2693Other tools
2694-----------
2695
73a1d050 2696There are numerous other tools, such as StGit, which exist for the
79c96c57 2697purpose of maintaining a patch series. These are outside of the scope of
b181d57f 2698this manual.
4c63ff45 2699
aa971cb9 2700[[problems-With-rewriting-history]]
4c63ff45
BF
2701Problems with rewriting history
2702-------------------------------
2703
b181d57f
BF
2704The primary problem with rewriting the history of a branch has to do
2705with merging. Suppose somebody fetches your branch and merges it into
2706their branch, with a result something like this:
2707
1dc71a91 2708................................................
b181d57f
BF
2709 o--o--O--o--o--o <-- origin
2710 \ \
2711 t--t--t--m <-- their branch:
1dc71a91 2712................................................
b181d57f
BF
2713
2714Then suppose you modify the last three commits:
2715
1dc71a91 2716................................................
b181d57f
BF
2717 o--o--o <-- new head of origin
2718 /
2719 o--o--O--o--o--o <-- old head of origin
1dc71a91 2720................................................
b181d57f
BF
2721
2722If we examined all this history together in one repository, it will
2723look like:
2724
1dc71a91 2725................................................
b181d57f
BF
2726 o--o--o <-- new head of origin
2727 /
2728 o--o--O--o--o--o <-- old head of origin
2729 \ \
2730 t--t--t--m <-- their branch:
1dc71a91 2731................................................
b181d57f
BF
2732
2733Git has no way of knowing that the new head is an updated version of
2734the old head; it treats this situation exactly the same as it would if
2735two developers had independently done the work on the old and new heads
2736in parallel. At this point, if someone attempts to merge the new head
2de9b711 2737in to their branch, Git will attempt to merge together the two (old and
b181d57f
BF
2738new) lines of development, instead of trying to replace the old by the
2739new. The results are likely to be unexpected.
2740
2741You may still choose to publish branches whose history is rewritten,
2742and it may be useful for others to be able to fetch those branches in
2743order to examine or test them, but they should not attempt to pull such
2744branches into their own work.
2745
2746For true distributed development that supports proper merging,
2747published branches should never be rewritten.
2748
3fb00282
SP
2749[[bisect-merges]]
2750Why bisecting merge commits can be harder than bisecting linear history
2751-----------------------------------------------------------------------
2752
5162e697 2753The linkgit:git-bisect[1] command correctly handles history that
3fb00282
SP
2754includes merge commits. However, when the commit that it finds is a
2755merge commit, the user may need to work harder than usual to figure out
2756why that commit introduced a problem.
2757
2758Imagine this history:
2759
2760................................................
2761 ---Z---o---X---...---o---A---C---D
2762 \ /
2763 o---o---Y---...---o---B
2764................................................
2765
2766Suppose that on the upper line of development, the meaning of one
2767of the functions that exists at Z is changed at commit X. The
2768commits from Z leading to A change both the function's
2769implementation and all calling sites that exist at Z, as well
2770as new calling sites they add, to be consistent. There is no
2771bug at A.
2772
2773Suppose that in the meantime on the lower line of development somebody
2774adds a new calling site for that function at commit Y. The
2775commits from Z leading to B all assume the old semantics of that
2776function and the callers and the callee are consistent with each
2777other. There is no bug at B, either.
2778
2779Suppose further that the two development lines merge cleanly at C,
2780so no conflict resolution is required.
2781
2782Nevertheless, the code at C is broken, because the callers added
2783on the lower line of development have not been converted to the new
2784semantics introduced on the upper line of development. So if all
2785you know is that D is bad, that Z is good, and that
5162e697 2786linkgit:git-bisect[1] identifies C as the culprit, how will you
3fb00282
SP
2787figure out that the problem is due to this change in semantics?
2788
6127c086 2789When the result of a `git bisect` is a non-merge commit, you should
3fb00282
SP
2790normally be able to discover the problem by examining just that commit.
2791Developers can make this easy by breaking their changes into small
2792self-contained commits. That won't help in the case above, however,
2793because the problem isn't obvious from examination of any single
2794commit; instead, a global view of the development is required. To
2795make matters worse, the change in semantics in the problematic
2796function may be just one small part of the changes in the upper
2797line of development.
2798
2799On the other hand, if instead of merging at C you had rebased the
2800history between Z to B on top of A, you would have gotten this
2801linear history:
2802
2803................................................................
2804 ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*
2805................................................................
2806
2807Bisecting between Z and D* would hit a single culprit commit Y*,
2808and understanding why Y* was broken would probably be easier.
2809
2de9b711 2810Partly for this reason, many experienced Git users, even when
3fb00282
SP
2811working on an otherwise merge-heavy project, keep the history
2812linear by rebasing against the latest upstream version before
2813publishing.
2814
e34caace 2815[[advanced-branch-management]]
b181d57f
BF
2816Advanced branch management
2817==========================
4c63ff45 2818
e34caace 2819[[fetching-individual-branches]]
b181d57f
BF
2820Fetching individual branches
2821----------------------------
2822
5162e697 2823Instead of using linkgit:git-remote[1], you can also choose just
b181d57f
BF
2824to update one branch at a time, and to store it locally under an
2825arbitrary name:
2826
2827-------------------------------------------------
2828$ git fetch origin todo:my-todo-work
2829-------------------------------------------------
2830
1249d8ad 2831The first argument, `origin`, just tells Git to fetch from the
2de9b711 2832repository you originally cloned from. The second argument tells Git
1249d8ad
TK
2833to fetch the branch named `todo` from the remote repository, and to
2834store it locally under the name `refs/heads/my-todo-work`.
b181d57f
BF
2835
2836You can also fetch branches from other repositories; so
2837
2838-------------------------------------------------
2839$ git fetch git://example.com/proj.git master:example-master
2840-------------------------------------------------
2841
1249d8ad
TK
2842will create a new branch named `example-master` and store in it the
2843branch named `master` from the repository at the given URL. If you
b181d57f 2844already have a branch named example-master, it will attempt to
59723040
BF
2845<<fast-forwards,fast-forward>> to the commit given by example.com's
2846master branch. In more detail:
b181d57f 2847
59723040
BF
2848[[fetch-fast-forwards]]
2849git fetch and fast-forwards
2850---------------------------
b181d57f 2851
1249d8ad 2852In the previous example, when updating an existing branch, `git fetch`
7a7d4ef6 2853checks to make sure that the most recent commit on the remote
b181d57f
BF
2854branch is a descendant of the most recent commit on your copy of the
2855branch before updating your copy of the branch to point at the new
a75d7b54 2856commit. Git calls this process a <<fast-forwards,fast-forward>>.
b181d57f 2857
a75d7b54 2858A fast-forward looks something like this:
b181d57f 2859
1dc71a91 2860................................................
b181d57f
BF
2861 o--o--o--o <-- old head of the branch
2862 \
2863 o--o--o <-- new head of the branch
1dc71a91 2864................................................
b181d57f
BF
2865
2866
2867In some cases it is possible that the new head will *not* actually be
2868a descendant of the old head. For example, the developer may have
2869realized she made a serious mistake, and decided to backtrack,
2870resulting in a situation like:
2871
1dc71a91 2872................................................
b181d57f
BF
2873 o--o--o--o--a--b <-- old head of the branch
2874 \
2875 o--o--o <-- new head of the branch
1dc71a91 2876................................................
b181d57f 2877
1249d8ad 2878In this case, `git fetch` will fail, and print out a warning.
b181d57f 2879
2de9b711 2880In that case, you can still force Git to update to the new head, as
b181d57f 2881described in the following section. However, note that in the
1249d8ad 2882situation above this may mean losing the commits labeled `a` and `b`,
b181d57f
BF
2883unless you've already created a reference of your own pointing to
2884them.
2885
e34caace 2886[[forcing-fetch]]
6127c086 2887Forcing git fetch to do non-fast-forward updates
b181d57f
BF
2888------------------------------------------------
2889
2890If git fetch fails because the new head of a branch is not a
2891descendant of the old head, you may force the update with:
2892
2893-------------------------------------------------
2894$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
2895-------------------------------------------------
2896
1249d8ad 2897Note the addition of the `+` sign. Alternatively, you can use the `-f`
c64415e2
BF
2898flag to force updates of all the fetched branches, as in:
2899
2900-------------------------------------------------
2901$ git fetch -f origin
2902-------------------------------------------------
2903
2904Be aware that commits that the old version of example/master pointed at
2905may be lost, as we saw in the previous section.
b181d57f 2906
e34caace 2907[[remote-branch-configuration]]
29b9a66f
MM
2908Configuring remote-tracking branches
2909------------------------------------
b181d57f 2910
1249d8ad 2911We saw above that `origin` is just a shortcut to refer to the
79c96c57 2912repository that you originally cloned from. This information is
2de9b711 2913stored in Git configuration variables, which you can see using
5162e697 2914linkgit:git-config[1]:
b181d57f
BF
2915
2916-------------------------------------------------
9d13bda3 2917$ git config -l
b181d57f
BF
2918core.repositoryformatversion=0
2919core.filemode=true
2920core.logallrefupdates=true
2921remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
2922remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
2923branch.master.remote=origin
2924branch.master.merge=refs/heads/master
2925-------------------------------------------------
2926
2927If there are other repositories that you also use frequently, you can
2928create similar configuration options to save typing; for example,
b181d57f
BF
2929
2930-------------------------------------------------
47adb8ac 2931$ git remote add example git://example.com/proj.git
b181d57f
BF
2932-------------------------------------------------
2933
47adb8ac 2934adds the following to `.git/config`:
b181d57f
BF
2935
2936-------------------------------------------------
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2937[remote "example"]
2938 url = git://example.com/proj.git
2939 fetch = +refs/heads/*:refs/remotes/example/*
b181d57f
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2940-------------------------------------------------
2941
47adb8ac
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2942Also note that the above configuration can be performed by directly
2943editing the file `.git/config` instead of using linkgit:git-remote[1].
b181d57f 2944
47adb8ac
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2945After configuring the remote, the following three commands will do the
2946same thing:
b181d57f
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2947
2948-------------------------------------------------
47adb8ac
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2949$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/*
2950$ git fetch example +refs/heads/*:refs/remotes/example/*
b181d57f
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2951$ git fetch example
2952-------------------------------------------------
2953
5162e697 2954See linkgit:git-config[1] for more details on the configuration
47adb8ac
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2955options mentioned above and linkgit:git-fetch[1] for more details on
2956the refspec syntax.
d19fbc3c 2957
d19fbc3c 2958
036f8199
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2959[[git-concepts]]
2960Git concepts
2961============
d19fbc3c 2962
036f8199
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2963Git is built on a small number of simple but powerful ideas. While it
2964is possible to get things done without understanding them, you will find
2de9b711 2965Git much more intuitive if you do.
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2966
2967We start with the most important, the <<def_object_database,object
2968database>> and the <<def_index,index>>.
b181d57f 2969
e34caace 2970[[the-object-database]]
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2971The Object Database
2972-------------------
2973
1bbf1c79
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2974
2975We already saw in <<understanding-commits>> that all commits are stored
2976under a 40-digit "object name". In fact, all the information needed to
2977represent the history of a project is stored in objects with such names.
a6e5ef7d
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2978In each case the name is calculated by taking the SHA-1 hash of the
2979contents of the object. The SHA-1 hash is a cryptographic hash function.
1bbf1c79
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2980What that means to us is that it is impossible to find two different
2981objects with the same name. This has a number of advantages; among
2982others:
2983
2984- Git can quickly determine whether two objects are identical or not,
2985 just by comparing names.
06ada152 2986- Since object names are computed the same way in every repository, the
1bbf1c79
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2987 same content stored in two repositories will always be stored under
2988 the same name.
2989- Git can detect errors when it reads an object, by checking that the
a6e5ef7d 2990 object's name is still the SHA-1 hash of its contents.
1bbf1c79
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2991
2992(See <<object-details>> for the details of the object formatting and
a6e5ef7d 2993SHA-1 calculation.)
1bbf1c79
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2994
2995There are four different types of objects: "blob", "tree", "commit", and
2996"tag".
2997
2998- A <<def_blob_object,"blob" object>> is used to store file data.
843c81dc 2999- A <<def_tree_object,"tree" object>> ties one or more
1bbf1c79
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3000 "blob" objects into a directory structure. In addition, a tree object
3001 can refer to other tree objects, thus creating a directory hierarchy.
3002- A <<def_commit_object,"commit" object>> ties such directory hierarchies
2ef8ac1b 3003 together into a <<def_DAG,directed acyclic graph>> of revisions--each
1bbf1c79
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3004 commit contains the object name of exactly one tree designating the
3005 directory hierarchy at the time of the commit. In addition, a commit
3006 refers to "parent" commit objects that describe the history of how we
3007 arrived at that directory hierarchy.
3008- A <<def_tag_object,"tag" object>> symbolically identifies and can be
3009 used to sign other objects. It contains the object name and type of
3010 another object, a symbolic name (of course!) and, optionally, a
3011 signature.
b181d57f 3012
b181d57f
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3013The object types in some more detail:
3014
513d419c
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3015[[commit-object]]
3016Commit Object
3017~~~~~~~~~~~~~
b181d57f 3018
1bbf1c79 3019The "commit" object links a physical state of a tree with a description
1249d8ad 3020of how we got there and why. Use the `--pretty=raw` option to
5162e697 3021linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite
1bbf1c79
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3022commit:
3023
3024------------------------------------------------
3025$ git show -s --pretty=raw 2be7fcb476
3026commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
3027tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
3028parent 257a84d9d02e90447b149af58b271c19405edb6a
3029author Dave Watson <dwatson@mimvista.com> 1187576872 -0400
3030committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700
3031
3032 Fix misspelling of 'suppress' in docs
3033
3034 Signed-off-by: Junio C Hamano <gitster@pobox.com>
3035------------------------------------------------
3036
3037As you can see, a commit is defined by:
3038
a6e5ef7d 3039- a tree: The SHA-1 name of a tree object (as defined below), representing
1bbf1c79 3040 the contents of a directory at a certain point in time.
edfbbf7e 3041- parent(s): The SHA-1 name(s) of some number of commits which represent the
9e5d87d4 3042 immediately previous step(s) in the history of the project. The
1bbf1c79
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3043 example above has one parent; merge commits may have more than
3044 one. A commit with no parents is called a "root" commit, and
3045 represents the initial revision of a project. Each project must have
3046 at least one root. A project can also have multiple roots, though
3047 that isn't common (or necessarily a good idea).
3048- an author: The name of the person responsible for this change, together
3049 with its date.
3050- a committer: The name of the person who actually created the commit,
3051 with the date it was done. This may be different from the author, for
3052 example, if the author was someone who wrote a patch and emailed it
3053 to the person who used it to create the commit.
3054- a comment describing this commit.
3055
3056Note that a commit does not itself contain any information about what
3057actually changed; all changes are calculated by comparing the contents
3058of the tree referred to by this commit with the trees associated with
2de9b711 3059its parents. In particular, Git does not attempt to record file renames
1bbf1c79
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3060explicitly, though it can identify cases where the existence of the same
3061file data at changing paths suggests a rename. (See, for example, the
1249d8ad 3062`-M` option to linkgit:git-diff[1]).
1bbf1c79 3063
5162e697 3064A commit is usually created by linkgit:git-commit[1], which creates a
1bbf1c79
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3065commit whose parent is normally the current HEAD, and whose tree is
3066taken from the content currently stored in the index.
b181d57f 3067
e34caace 3068[[tree-object]]
b181d57f 3069Tree Object
971aa71f 3070~~~~~~~~~~~
b181d57f 3071
5162e697
DM
3072The ever-versatile linkgit:git-show[1] command can also be used to
3073examine tree objects, but linkgit:git-ls-tree[1] will give you more
1bbf1c79
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3074details:
3075
3076------------------------------------------------
3077$ git ls-tree fb3a8bdd0ce
3078100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
3079100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
3080100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
3081040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
3082100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
3083100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
3084100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
3085100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
3086...
3087------------------------------------------------
3088
3089As you can see, a tree object contains a list of entries, each with a
a6e5ef7d 3090mode, object type, SHA-1 name, and name, sorted by name. It represents
1bbf1c79
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3091the contents of a single directory tree.
3092
3093The object type may be a blob, representing the contents of a file, or
3094another tree, representing the contents of a subdirectory. Since trees
a6e5ef7d
FC
3095and blobs, like all other objects, are named by the SHA-1 hash of their
3096contents, two trees have the same SHA-1 name if and only if their
1bbf1c79 3097contents (including, recursively, the contents of all subdirectories)
2de9b711 3098are identical. This allows Git to quickly determine the differences
1bbf1c79
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3099between two related tree objects, since it can ignore any entries with
3100identical object names.
3101
3102(Note: in the presence of submodules, trees may also have commits as
6dd14366 3103entries. See <<submodules>> for documentation.)
1bbf1c79 3104
2de9b711 3105Note that the files all have mode 644 or 755: Git actually only pays
1bbf1c79 3106attention to the executable bit.
b181d57f 3107
513d419c
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3108[[blob-object]]
3109Blob Object
3110~~~~~~~~~~~
b181d57f 3111
5162e697 3112You can use linkgit:git-show[1] to examine the contents of a blob; take,
1249d8ad 3113for example, the blob in the entry for `COPYING` from the tree above:
b181d57f 3114
1bbf1c79
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3115------------------------------------------------
3116$ git show 6ff87c4664
3117
3118 Note that the only valid version of the GPL as far as this project
3119 is concerned is _this_ particular version of the license (ie v2, not
3120 v2.2 or v3.x or whatever), unless explicitly otherwise stated.
3121...
3122------------------------------------------------
b181d57f 3123
1bbf1c79
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3124A "blob" object is nothing but a binary blob of data. It doesn't refer
3125to anything else or have attributes of any kind.
3126
3127Since the blob is entirely defined by its data, if two files in a
3128directory tree (or in multiple different versions of the repository)
3129have the same contents, they will share the same blob object. The object
3130is totally independent of its location in the directory tree, and
3131renaming a file does not change the object that file is associated with.
3132
3133Note that any tree or blob object can be examined using
5162e697 3134linkgit:git-show[1] with the <revision>:<path> syntax. This can
1bbf1c79
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3135sometimes be useful for browsing the contents of a tree that is not
3136currently checked out.
b181d57f 3137
e34caace 3138[[trust]]
b181d57f 3139Trust
971aa71f 3140~~~~~
b181d57f 3141
a6e5ef7d 3142If you receive the SHA-1 name of a blob from one source, and its contents
1bbf1c79 3143from another (possibly untrusted) source, you can still trust that those
a6e5ef7d
FC
3144contents are correct as long as the SHA-1 name agrees. This is becaus