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0eb4f7cd 1Git User's Manual (for version 1.5.3 or newer)
71f4b183 2______________________________________________
d19fbc3c 3
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4
5Git is a fast distributed revision control system.
6
02783075 7This manual is designed to be readable by someone with basic UNIX
79c96c57 8command-line skills, but no previous knowledge of git.
d19fbc3c 9
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10<<repositories-and-branches>> and <<exploring-git-history>> explain how
11to fetch and study a project using git--read these chapters to learn how
12to build and test a particular version of a software project, search for
13regressions, and so on.
ef89f701 14
2624d9a5 15People needing to do actual development will also want to read
aa971cb9 16<<Developing-With-git>> and <<sharing-development>>.
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17
18Further chapters cover more specialized topics.
19
d19fbc3c 20Comprehensive reference documentation is available through the man
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21pages, or linkgit:git-help[1] command. For example, for the command
22"git clone <repo>", you can either use:
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23
24------------------------------------------------
25$ man git-clone
26------------------------------------------------
27
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28or:
29
30------------------------------------------------
31$ git help clone
32------------------------------------------------
33
34With the latter, you can use the manual viewer of your choice; see
35linkgit:git-help[1] for more information.
36
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37See also <<git-quick-start>> for a brief overview of git commands,
38without any explanation.
b181d57f 39
99f171bb 40Finally, see <<todo>> for ways that you can help make this manual more
2624d9a5 41complete.
b181d57f 42
b181d57f 43
e34caace 44[[repositories-and-branches]]
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45Repositories and Branches
46=========================
47
e34caace 48[[how-to-get-a-git-repository]]
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49How to get a git repository
50---------------------------
51
52It will be useful to have a git repository to experiment with as you
53read this manual.
54
5162e697 55The best way to get one is by using the linkgit:git-clone[1] command to
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56download a copy of an existing repository. If you don't already have a
57project in mind, here are some interesting examples:
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58
59------------------------------------------------
60 # git itself (approx. 10MB download):
61$ git clone git://git.kernel.org/pub/scm/git/git.git
c7719fbe 62 # the Linux kernel (approx. 150MB download):
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63$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
64------------------------------------------------
65
66The initial clone may be time-consuming for a large project, but you
67will only need to clone once.
68
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69The clone command creates a new directory named after the project ("git"
70or "linux-2.6" in the examples above). After you cd into this
d19fbc3c 71directory, you will see that it contains a copy of the project files,
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72called the <<def_working_tree,working tree>>, together with a special
73top-level directory named ".git", which contains all the information
74about the history of the project.
d19fbc3c 75
e34caace 76[[how-to-check-out]]
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77How to check out a different version of a project
78-------------------------------------------------
79
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80Git is best thought of as a tool for storing the history of a collection
81of files. It stores the history as a compressed collection of
82interrelated snapshots of the project's contents. In git each such
83version is called a <<def_commit,commit>>.
d19fbc3c 84
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85Those snapshots aren't necessarily all arranged in a single line from
86oldest to newest; instead, work may simultaneously proceed along
57283291 87parallel lines of development, called <<def_branch,branches>>, which may
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88merge and diverge.
89
90A single git repository can track development on multiple branches. It
91does this by keeping a list of <<def_head,heads>> which reference the
5162e697 92latest commit on each branch; the linkgit:git-branch[1] command shows
81b6c950 93you the list of branch heads:
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94
95------------------------------------------------
96$ git branch
97* master
98------------------------------------------------
99
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100A freshly cloned repository contains a single branch head, by default
101named "master", with the working directory initialized to the state of
102the project referred to by that branch head.
d19fbc3c 103
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104Most projects also use <<def_tag,tags>>. Tags, like heads, are
105references into the project's history, and can be listed using the
5162e697 106linkgit:git-tag[1] command:
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107
108------------------------------------------------
109$ git tag -l
110v2.6.11
111v2.6.11-tree
112v2.6.12
113v2.6.12-rc2
114v2.6.12-rc3
115v2.6.12-rc4
116v2.6.12-rc5
117v2.6.12-rc6
118v2.6.13
119...
120------------------------------------------------
121
fe4b3e59 122Tags are expected to always point at the same version of a project,
81b6c950 123while heads are expected to advance as development progresses.
fe4b3e59 124
81b6c950 125Create a new branch head pointing to one of these versions and check it
5162e697 126out using linkgit:git-checkout[1]:
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127
128------------------------------------------------
129$ git checkout -b new v2.6.13
130------------------------------------------------
131
132The working directory then reflects the contents that the project had
5162e697 133when it was tagged v2.6.13, and linkgit:git-branch[1] shows two
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134branches, with an asterisk marking the currently checked-out branch:
135
136------------------------------------------------
137$ git branch
138 master
139* new
140------------------------------------------------
141
142If you decide that you'd rather see version 2.6.17, you can modify
143the current branch to point at v2.6.17 instead, with
144
145------------------------------------------------
146$ git reset --hard v2.6.17
147------------------------------------------------
148
81b6c950 149Note that if the current branch head was your only reference to a
d19fbc3c 150particular point in history, then resetting that branch may leave you
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151with no way to find the history it used to point to; so use this command
152carefully.
d19fbc3c 153
e34caace 154[[understanding-commits]]
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155Understanding History: Commits
156------------------------------
157
158Every change in the history of a project is represented by a commit.
5162e697 159The linkgit:git-show[1] command shows the most recent commit on the
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160current branch:
161
162------------------------------------------------
163$ git show
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164commit 17cf781661e6d38f737f15f53ab552f1e95960d7
165Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)>
166Date: Tue Apr 19 14:11:06 2005 -0700
167
168 Remove duplicate getenv(DB_ENVIRONMENT) call
169
170 Noted by Tony Luck.
171
172diff --git a/init-db.c b/init-db.c
173index 65898fa..b002dc6 100644
174--- a/init-db.c
175+++ b/init-db.c
176@@ -7,7 +7,7 @@
d19fbc3c 177
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178 int main(int argc, char **argv)
179 {
180- char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
181+ char *sha1_dir, *path;
182 int len, i;
183
184 if (mkdir(".git", 0755) < 0) {
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185------------------------------------------------
186
187As you can see, a commit shows who made the latest change, what they
188did, and why.
189
35121930 190Every commit has a 40-hexdigit id, sometimes called the "object name" or the
a6e5ef7d 191"SHA-1 id", shown on the first line of the "git show" output. You can usually
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192refer to a commit by a shorter name, such as a tag or a branch name, but this
193longer name can also be useful. Most importantly, it is a globally unique
194name for this commit: so if you tell somebody else the object name (for
195example in email), then you are guaranteed that name will refer to the same
196commit in their repository that it does in yours (assuming their repository
197has that commit at all). Since the object name is computed as a hash over the
198contents of the commit, you are guaranteed that the commit can never change
199without its name also changing.
200
036f8199 201In fact, in <<git-concepts>> we shall see that everything stored in git
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202history, including file data and directory contents, is stored in an object
203with a name that is a hash of its contents.
d19fbc3c 204
e34caace 205[[understanding-reachability]]
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206Understanding history: commits, parents, and reachability
207~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
208
209Every commit (except the very first commit in a project) also has a
210parent commit which shows what happened before this commit.
211Following the chain of parents will eventually take you back to the
212beginning of the project.
213
214However, the commits do not form a simple list; git allows lines of
215development to diverge and then reconverge, and the point where two
216lines of development reconverge is called a "merge". The commit
217representing a merge can therefore have more than one parent, with
218each parent representing the most recent commit on one of the lines
219of development leading to that point.
220
5162e697 221The best way to see how this works is using the linkgit:gitk[1]
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222command; running gitk now on a git repository and looking for merge
223commits will help understand how the git organizes history.
224
225In the following, we say that commit X is "reachable" from commit Y
226if commit X is an ancestor of commit Y. Equivalently, you could say
02783075 227that Y is a descendant of X, or that there is a chain of parents
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228leading from commit Y to commit X.
229
e34caace 230[[history-diagrams]]
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231Understanding history: History diagrams
232~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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233
234We will sometimes represent git history using diagrams like the one
235below. Commits are shown as "o", and the links between them with
236lines drawn with - / and \. Time goes left to right:
237
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238
239................................................
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240 o--o--o <-- Branch A
241 /
242 o--o--o <-- master
243 \
244 o--o--o <-- Branch B
1dc71a91 245................................................
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246
247If we need to talk about a particular commit, the character "o" may
248be replaced with another letter or number.
249
e34caace 250[[what-is-a-branch]]
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251Understanding history: What is a branch?
252~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
253
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254When we need to be precise, we will use the word "branch" to mean a line
255of development, and "branch head" (or just "head") to mean a reference
256to the most recent commit on a branch. In the example above, the branch
257head named "A" is a pointer to one particular commit, but we refer to
258the line of three commits leading up to that point as all being part of
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259"branch A".
260
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261However, when no confusion will result, we often just use the term
262"branch" both for branches and for branch heads.
d19fbc3c 263
e34caace 264[[manipulating-branches]]
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265Manipulating branches
266---------------------
267
268Creating, deleting, and modifying branches is quick and easy; here's
269a summary of the commands:
270
271git branch::
272 list all branches
273git branch <branch>::
274 create a new branch named <branch>, referencing the same
275 point in history as the current branch
276git branch <branch> <start-point>::
277 create a new branch named <branch>, referencing
278 <start-point>, which may be specified any way you like,
279 including using a branch name or a tag name
280git branch -d <branch>::
281 delete the branch <branch>; if the branch you are deleting
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282 points to a commit which is not reachable from the current
283 branch, this command will fail with a warning.
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284git branch -D <branch>::
285 even if the branch points to a commit not reachable
286 from the current branch, you may know that that commit
287 is still reachable from some other branch or tag. In that
288 case it is safe to use this command to force git to delete
289 the branch.
290git checkout <branch>::
291 make the current branch <branch>, updating the working
292 directory to reflect the version referenced by <branch>
293git checkout -b <new> <start-point>::
294 create a new branch <new> referencing <start-point>, and
295 check it out.
296
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297The special symbol "HEAD" can always be used to refer to the current
298branch. In fact, git uses a file named "HEAD" in the .git directory to
299remember which branch is current:
300
301------------------------------------------------
302$ cat .git/HEAD
303ref: refs/heads/master
304------------------------------------------------
305
25d9f3fa 306[[detached-head]]
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307Examining an old version without creating a new branch
308------------------------------------------------------
309
6127c086 310The `git checkout` command normally expects a branch head, but will also
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311accept an arbitrary commit; for example, you can check out the commit
312referenced by a tag:
313
314------------------------------------------------
315$ git checkout v2.6.17
316Note: moving to "v2.6.17" which isn't a local branch
317If you want to create a new branch from this checkout, you may do so
318(now or later) by using -b with the checkout command again. Example:
319 git checkout -b <new_branch_name>
320HEAD is now at 427abfa... Linux v2.6.17
321------------------------------------------------
322
a6e5ef7d 323The HEAD then refers to the SHA-1 of the commit instead of to a branch,
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324and git branch shows that you are no longer on a branch:
325
326------------------------------------------------
327$ cat .git/HEAD
328427abfa28afedffadfca9dd8b067eb6d36bac53f
953f3d6f 329$ git branch
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330* (no branch)
331 master
332------------------------------------------------
333
334In this case we say that the HEAD is "detached".
335
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336This is an easy way to check out a particular version without having to
337make up a name for the new branch. You can still create a new branch
338(or tag) for this version later if you decide to.
d19fbc3c 339
e34caace 340[[examining-remote-branches]]
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341Examining branches from a remote repository
342-------------------------------------------
343
344The "master" branch that was created at the time you cloned is a copy
345of the HEAD in the repository that you cloned from. That repository
346may also have had other branches, though, and your local repository
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347keeps branches which track each of those remote branches, called
348remote-tracking branches, which you
5162e697 349can view using the "-r" option to linkgit:git-branch[1]:
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350
351------------------------------------------------
352$ git branch -r
353 origin/HEAD
354 origin/html
355 origin/maint
356 origin/man
357 origin/master
358 origin/next
359 origin/pu
360 origin/todo
361------------------------------------------------
362
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363In this example, "origin" is called a remote repository, or "remote"
364for short. The branches of this repository are called "remote
365branches" from our point of view. The remote-tracking branches listed
366above were created based on the remote branches at clone time and will
367be updated by "git fetch" (hence "git pull") and "git push". See
368<<Updating-a-repository-With-git-fetch>> for details.
369
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370You might want to build on one of these remote-tracking branches
371on a branch of your own, just as you would for a tag:
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372
373------------------------------------------------
374$ git checkout -b my-todo-copy origin/todo
375------------------------------------------------
376
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377You can also check out "origin/todo" directly to examine it or
378write a one-off patch. See <<detached-head,detached head>>.
379
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380Note that the name "origin" is just the name that git uses by default
381to refer to the repository that you cloned from.
382
383[[how-git-stores-references]]
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384Naming branches, tags, and other references
385-------------------------------------------
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386
387Branches, remote-tracking branches, and tags are all references to
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388commits. All references are named with a slash-separated path name
389starting with "refs"; the names we've been using so far are actually
390shorthand:
d19fbc3c 391
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392 - The branch "test" is short for "refs/heads/test".
393 - The tag "v2.6.18" is short for "refs/tags/v2.6.18".
394 - "origin/master" is short for "refs/remotes/origin/master".
d19fbc3c 395
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396The full name is occasionally useful if, for example, there ever
397exists a tag and a branch with the same name.
d19fbc3c 398
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399(Newly created refs are actually stored in the .git/refs directory,
400under the path given by their name. However, for efficiency reasons
401they may also be packed together in a single file; see
5162e697 402linkgit:git-pack-refs[1]).
fc74ecc1 403
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404As another useful shortcut, the "HEAD" of a repository can be referred
405to just using the name of that repository. So, for example, "origin"
406is usually a shortcut for the HEAD branch in the repository "origin".
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407
408For the complete list of paths which git checks for references, and
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409the order it uses to decide which to choose when there are multiple
410references with the same shorthand name, see the "SPECIFYING
9d83e382 411REVISIONS" section of linkgit:gitrevisions[7].
d19fbc3c 412
aa971cb9 413[[Updating-a-repository-With-git-fetch]]
6127c086 414Updating a repository with git fetch
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415------------------------------------
416
417Eventually the developer cloned from will do additional work in her
418repository, creating new commits and advancing the branches to point
419at the new commits.
420
421The command "git fetch", with no arguments, will update all of the
422remote-tracking branches to the latest version found in her
423repository. It will not touch any of your own branches--not even the
424"master" branch that was created for you on clone.
425
e34caace 426[[fetching-branches]]
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427Fetching branches from other repositories
428-----------------------------------------
429
430You can also track branches from repositories other than the one you
5162e697 431cloned from, using linkgit:git-remote[1]:
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432
433-------------------------------------------------
434$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git
04483524 435$ git fetch linux-nfs
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436* refs/remotes/linux-nfs/master: storing branch 'master' ...
437 commit: bf81b46
438-------------------------------------------------
439
440New remote-tracking branches will be stored under the shorthand name
6127c086 441that you gave "git remote add", in this case linux-nfs:
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442
443-------------------------------------------------
444$ git branch -r
445linux-nfs/master
446origin/master
447-------------------------------------------------
448
8b3f3f84 449If you run "git fetch <remote>" later, the remote-tracking branches for the
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450named <remote> will be updated.
451
452If you examine the file .git/config, you will see that git has added
453a new stanza:
454
455-------------------------------------------------
456$ cat .git/config
457...
458[remote "linux-nfs"]
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459 url = git://linux-nfs.org/pub/nfs-2.6.git
460 fetch = +refs/heads/*:refs/remotes/linux-nfs/*
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461...
462-------------------------------------------------
463
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464This is what causes git to track the remote's branches; you may modify
465or delete these configuration options by editing .git/config with a
466text editor. (See the "CONFIGURATION FILE" section of
5162e697 467linkgit:git-config[1] for details.)
d5cd5de4 468
e34caace 469[[exploring-git-history]]
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470Exploring git history
471=====================
472
473Git is best thought of as a tool for storing the history of a
474collection of files. It does this by storing compressed snapshots of
1130845b 475the contents of a file hierarchy, together with "commits" which show
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476the relationships between these snapshots.
477
478Git provides extremely flexible and fast tools for exploring the
479history of a project.
480
aacd404e 481We start with one specialized tool that is useful for finding the
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482commit that introduced a bug into a project.
483
e34caace 484[[using-bisect]]
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485How to use bisect to find a regression
486--------------------------------------
487
488Suppose version 2.6.18 of your project worked, but the version at
489"master" crashes. Sometimes the best way to find the cause of such a
490regression is to perform a brute-force search through the project's
491history to find the particular commit that caused the problem. The
5162e697 492linkgit:git-bisect[1] command can help you do this:
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493
494-------------------------------------------------
495$ git bisect start
496$ git bisect good v2.6.18
497$ git bisect bad master
498Bisecting: 3537 revisions left to test after this
499[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]
500-------------------------------------------------
501
502If you run "git branch" at this point, you'll see that git has
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503temporarily moved you in "(no branch)". HEAD is now detached from any
504branch and points directly to a commit (with commit id 65934...) that
505is reachable from "master" but not from v2.6.18. Compile and test it,
506and see whether it crashes. Assume it does crash. Then:
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507
508-------------------------------------------------
509$ git bisect bad
510Bisecting: 1769 revisions left to test after this
511[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
512-------------------------------------------------
513
514checks out an older version. Continue like this, telling git at each
515stage whether the version it gives you is good or bad, and notice
516that the number of revisions left to test is cut approximately in
517half each time.
518
519After about 13 tests (in this case), it will output the commit id of
520the guilty commit. You can then examine the commit with
5162e697 521linkgit:git-show[1], find out who wrote it, and mail them your bug
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522report with the commit id. Finally, run
523
524-------------------------------------------------
525$ git bisect reset
526-------------------------------------------------
527
0e25790f 528to return you to the branch you were on before.
d19fbc3c 529
6127c086 530Note that the version which `git bisect` checks out for you at each
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531point is just a suggestion, and you're free to try a different
532version if you think it would be a good idea. For example,
533occasionally you may land on a commit that broke something unrelated;
534run
535
536-------------------------------------------------
04483524 537$ git bisect visualize
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538-------------------------------------------------
539
540which will run gitk and label the commit it chose with a marker that
843c81dc 541says "bisect". Choose a safe-looking commit nearby, note its commit
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542id, and check it out with:
543
544-------------------------------------------------
545$ git reset --hard fb47ddb2db...
546-------------------------------------------------
547
548then test, run "bisect good" or "bisect bad" as appropriate, and
549continue.
550
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551Instead of "git bisect visualize" and then "git reset --hard
552fb47ddb2db...", you might just want to tell git that you want to skip
553the current commit:
554
555-------------------------------------------------
556$ git bisect skip
557-------------------------------------------------
558
559In this case, though, git may not eventually be able to tell the first
a0178ae2 560bad one between some first skipped commits and a later bad commit.
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561
562There are also ways to automate the bisecting process if you have a
563test script that can tell a good from a bad commit. See
564linkgit:git-bisect[1] for more information about this and other "git
565bisect" features.
566
e34caace 567[[naming-commits]]
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568Naming commits
569--------------
570
571We have seen several ways of naming commits already:
572
d55ae921 573 - 40-hexdigit object name
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574 - branch name: refers to the commit at the head of the given
575 branch
576 - tag name: refers to the commit pointed to by the given tag
577 (we've seen branches and tags are special cases of
578 <<how-git-stores-references,references>>).
579 - HEAD: refers to the head of the current branch
580
eb6ae7f4 581There are many more; see the "SPECIFYING REVISIONS" section of the
9d83e382 582linkgit:gitrevisions[7] man page for the complete list of ways to
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583name revisions. Some examples:
584
585-------------------------------------------------
d55ae921 586$ git show fb47ddb2 # the first few characters of the object name
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587 # are usually enough to specify it uniquely
588$ git show HEAD^ # the parent of the HEAD commit
589$ git show HEAD^^ # the grandparent
590$ git show HEAD~4 # the great-great-grandparent
591-------------------------------------------------
592
593Recall that merge commits may have more than one parent; by default,
594^ and ~ follow the first parent listed in the commit, but you can
595also choose:
596
597-------------------------------------------------
598$ git show HEAD^1 # show the first parent of HEAD
599$ git show HEAD^2 # show the second parent of HEAD
600-------------------------------------------------
601
602In addition to HEAD, there are several other special names for
603commits:
604
605Merges (to be discussed later), as well as operations such as
6127c086 606`git reset`, which change the currently checked-out commit, generally
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607set ORIG_HEAD to the value HEAD had before the current operation.
608
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609The `git fetch` operation always stores the head of the last fetched
610branch in FETCH_HEAD. For example, if you run `git fetch` without
d19fbc3c
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611specifying a local branch as the target of the operation
612
613-------------------------------------------------
614$ git fetch git://example.com/proj.git theirbranch
615-------------------------------------------------
616
617the fetched commits will still be available from FETCH_HEAD.
618
619When we discuss merges we'll also see the special name MERGE_HEAD,
620which refers to the other branch that we're merging in to the current
621branch.
622
5162e697 623The linkgit:git-rev-parse[1] command is a low-level command that is
d55ae921
BF
624occasionally useful for translating some name for a commit to the object
625name for that commit:
aec053bb
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626
627-------------------------------------------------
628$ git rev-parse origin
629e05db0fd4f31dde7005f075a84f96b360d05984b
630-------------------------------------------------
631
e34caace 632[[creating-tags]]
d19fbc3c
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633Creating tags
634-------------
635
636We can also create a tag to refer to a particular commit; after
637running
638
639-------------------------------------------------
04483524 640$ git tag stable-1 1b2e1d63ff
d19fbc3c
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641-------------------------------------------------
642
643You can use stable-1 to refer to the commit 1b2e1d63ff.
644
c64415e2
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645This creates a "lightweight" tag. If you would also like to include a
646comment with the tag, and possibly sign it cryptographically, then you
5162e697 647should create a tag object instead; see the linkgit:git-tag[1] man page
c64415e2 648for details.
d19fbc3c 649
e34caace 650[[browsing-revisions]]
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651Browsing revisions
652------------------
653
5162e697 654The linkgit:git-log[1] command can show lists of commits. On its
d19fbc3c
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655own, it shows all commits reachable from the parent commit; but you
656can also make more specific requests:
657
658-------------------------------------------------
659$ git log v2.5.. # commits since (not reachable from) v2.5
660$ git log test..master # commits reachable from master but not test
661$ git log master..test # ...reachable from test but not master
662$ git log master...test # ...reachable from either test or master,
663 # but not both
664$ git log --since="2 weeks ago" # commits from the last 2 weeks
665$ git log Makefile # commits which modify Makefile
666$ git log fs/ # ... which modify any file under fs/
667$ git log -S'foo()' # commits which add or remove any file data
668 # matching the string 'foo()'
669-------------------------------------------------
670
671And of course you can combine all of these; the following finds
672commits since v2.5 which touch the Makefile or any file under fs:
673
674-------------------------------------------------
675$ git log v2.5.. Makefile fs/
676-------------------------------------------------
677
678You can also ask git log to show patches:
679
680-------------------------------------------------
681$ git log -p
682-------------------------------------------------
683
5162e697 684See the "--pretty" option in the linkgit:git-log[1] man page for more
d19fbc3c
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685display options.
686
687Note that git log starts with the most recent commit and works
688backwards through the parents; however, since git history can contain
3dff5379 689multiple independent lines of development, the particular order that
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690commits are listed in may be somewhat arbitrary.
691
e34caace 692[[generating-diffs]]
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693Generating diffs
694----------------
695
696You can generate diffs between any two versions using
5162e697 697linkgit:git-diff[1]:
d19fbc3c
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698
699-------------------------------------------------
700$ git diff master..test
701-------------------------------------------------
702
5b98d9bc
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703That will produce the diff between the tips of the two branches. If
704you'd prefer to find the diff from their common ancestor to test, you
705can use three dots instead of two:
706
707-------------------------------------------------
708$ git diff master...test
709-------------------------------------------------
710
711Sometimes what you want instead is a set of patches; for this you can
5162e697 712use linkgit:git-format-patch[1]:
d19fbc3c
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713
714-------------------------------------------------
715$ git format-patch master..test
716-------------------------------------------------
717
718will generate a file with a patch for each commit reachable from test
5b98d9bc 719but not from master.
d19fbc3c 720
e34caace 721[[viewing-old-file-versions]]
d19fbc3c
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722Viewing old file versions
723-------------------------
724
725You can always view an old version of a file by just checking out the
726correct revision first. But sometimes it is more convenient to be
727able to view an old version of a single file without checking
728anything out; this command does that:
729
730-------------------------------------------------
731$ git show v2.5:fs/locks.c
732-------------------------------------------------
733
734Before the colon may be anything that names a commit, and after it
735may be any path to a file tracked by git.
736
e34caace 737[[history-examples]]
aec053bb
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738Examples
739--------
740
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741[[counting-commits-on-a-branch]]
742Counting the number of commits on a branch
743~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
744
745Suppose you want to know how many commits you've made on "mybranch"
746since it diverged from "origin":
747
748-------------------------------------------------
749$ git log --pretty=oneline origin..mybranch | wc -l
750-------------------------------------------------
751
752Alternatively, you may often see this sort of thing done with the
a6e5ef7d 753lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's
46acd3fa
BF
754of all the given commits:
755
756-------------------------------------------------
757$ git rev-list origin..mybranch | wc -l
758-------------------------------------------------
759
e34caace 760[[checking-for-equal-branches]]
aec053bb 761Check whether two branches point at the same history
2f99710c 762~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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763
764Suppose you want to check whether two branches point at the same point
765in history.
766
767-------------------------------------------------
768$ git diff origin..master
769-------------------------------------------------
770
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771will tell you whether the contents of the project are the same at the
772two branches; in theory, however, it's possible that the same project
773contents could have been arrived at by two different historical
d55ae921 774routes. You could compare the object names:
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775
776-------------------------------------------------
777$ git rev-list origin
778e05db0fd4f31dde7005f075a84f96b360d05984b
779$ git rev-list master
780e05db0fd4f31dde7005f075a84f96b360d05984b
781-------------------------------------------------
782
69f7ad73
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783Or you could recall that the ... operator selects all commits
784contained reachable from either one reference or the other but not
ddd2369c 785both; so
aec053bb
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786
787-------------------------------------------------
788$ git log origin...master
789-------------------------------------------------
790
791will return no commits when the two branches are equal.
792
e34caace 793[[finding-tagged-descendants]]
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794Find first tagged version including a given fix
795~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
aec053bb 796
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797Suppose you know that the commit e05db0fd fixed a certain problem.
798You'd like to find the earliest tagged release that contains that
799fix.
800
801Of course, there may be more than one answer--if the history branched
802after commit e05db0fd, then there could be multiple "earliest" tagged
803releases.
804
805You could just visually inspect the commits since e05db0fd:
806
807-------------------------------------------------
808$ gitk e05db0fd..
809-------------------------------------------------
810
5162e697 811Or you can use linkgit:git-name-rev[1], which will give the commit a
b181d57f
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812name based on any tag it finds pointing to one of the commit's
813descendants:
814
815-------------------------------------------------
04483524 816$ git name-rev --tags e05db0fd
b181d57f
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817e05db0fd tags/v1.5.0-rc1^0~23
818-------------------------------------------------
819
5162e697 820The linkgit:git-describe[1] command does the opposite, naming the
b181d57f
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821revision using a tag on which the given commit is based:
822
823-------------------------------------------------
824$ git describe e05db0fd
04483524 825v1.5.0-rc0-260-ge05db0f
b181d57f
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826-------------------------------------------------
827
828but that may sometimes help you guess which tags might come after the
829given commit.
830
831If you just want to verify whether a given tagged version contains a
5162e697 832given commit, you could use linkgit:git-merge-base[1]:
b181d57f
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833
834-------------------------------------------------
835$ git merge-base e05db0fd v1.5.0-rc1
836e05db0fd4f31dde7005f075a84f96b360d05984b
837-------------------------------------------------
838
839The merge-base command finds a common ancestor of the given commits,
840and always returns one or the other in the case where one is a
841descendant of the other; so the above output shows that e05db0fd
842actually is an ancestor of v1.5.0-rc1.
843
844Alternatively, note that
845
846-------------------------------------------------
4a7979ca 847$ git log v1.5.0-rc1..e05db0fd
b181d57f
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848-------------------------------------------------
849
4a7979ca 850will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
b181d57f 851because it outputs only commits that are not reachable from v1.5.0-rc1.
aec053bb 852
5162e697 853As yet another alternative, the linkgit:git-show-branch[1] command lists
4a7979ca
BF
854the commits reachable from its arguments with a display on the left-hand
855side that indicates which arguments that commit is reachable from. So,
856you can run something like
857
858-------------------------------------------------
859$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
860! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
861available
862 ! [v1.5.0-rc0] GIT v1.5.0 preview
863 ! [v1.5.0-rc1] GIT v1.5.0-rc1
864 ! [v1.5.0-rc2] GIT v1.5.0-rc2
865...
866-------------------------------------------------
867
868then search for a line that looks like
869
870-------------------------------------------------
871+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
872available
873-------------------------------------------------
874
875Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and
876from v1.5.0-rc2, but not from v1.5.0-rc0.
877
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878[[showing-commits-unique-to-a-branch]]
879Showing commits unique to a given branch
880~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4a7979ca 881
629d9f78
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882Suppose you would like to see all the commits reachable from the branch
883head named "master" but not from any other head in your repository.
d19fbc3c 884
629d9f78 885We can list all the heads in this repository with
5162e697 886linkgit:git-show-ref[1]:
d19fbc3c 887
629d9f78
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888-------------------------------------------------
889$ git show-ref --heads
890bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial
891db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint
892a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master
89324dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2
8941e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes
895-------------------------------------------------
d19fbc3c 896
629d9f78
BF
897We can get just the branch-head names, and remove "master", with
898the help of the standard utilities cut and grep:
899
900-------------------------------------------------
901$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'
902refs/heads/core-tutorial
903refs/heads/maint
904refs/heads/tutorial-2
905refs/heads/tutorial-fixes
906-------------------------------------------------
907
908And then we can ask to see all the commits reachable from master
909but not from these other heads:
910
911-------------------------------------------------
912$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |
913 grep -v '^refs/heads/master' )
914-------------------------------------------------
915
916Obviously, endless variations are possible; for example, to see all
917commits reachable from some head but not from any tag in the repository:
918
919-------------------------------------------------
c78974f7 920$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )
629d9f78
BF
921-------------------------------------------------
922
9d83e382 923(See linkgit:gitrevisions[7] for explanations of commit-selecting
629d9f78
BF
924syntax such as `--not`.)
925
82c8bf28
BF
926[[making-a-release]]
927Creating a changelog and tarball for a software release
928~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
929
5162e697 930The linkgit:git-archive[1] command can create a tar or zip archive from
82c8bf28
BF
931any version of a project; for example:
932
933-------------------------------------------------
7ed1690c 934$ git archive -o latest.tar.gz --prefix=project/ HEAD
82c8bf28
BF
935-------------------------------------------------
936
7ed1690c
TK
937will use HEAD to produce a gzipped tar archive in which each filename
938is preceded by `project/`. The output file format is inferred from
939the output file extension if possible, see linkgit:git-archive[1] for
940details.
941
942Versions of Git older than 1.7.7 don't know about the 'tar.gz' format,
943you'll need to use gzip explicitly:
944
945-------------------------------------------------
946$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz
947-------------------------------------------------
82c8bf28
BF
948
949If you're releasing a new version of a software project, you may want
950to simultaneously make a changelog to include in the release
951announcement.
952
953Linus Torvalds, for example, makes new kernel releases by tagging them,
954then running:
955
956-------------------------------------------------
957$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7
958-------------------------------------------------
959
960where release-script is a shell script that looks like:
961
962-------------------------------------------------
963#!/bin/sh
964stable="$1"
965last="$2"
966new="$3"
967echo "# git tag v$new"
968echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz"
969echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz"
970echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new"
971echo "git shortlog --no-merges v$new ^v$last > ../ShortLog"
972echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new"
973-------------------------------------------------
974
975and then he just cut-and-pastes the output commands after verifying that
976they look OK.
4a7979ca 977
e1ba4c32 978[[Finding-commits-With-given-Content]]
187b0d80 979Finding commits referencing a file with given content
d5821de2 980~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
187b0d80
BF
981
982Somebody hands you a copy of a file, and asks which commits modified a
983file such that it contained the given content either before or after the
984commit. You can find out with this:
985
986-------------------------------------------------
477ff5b7 987$ git log --raw --abbrev=40 --pretty=oneline |
187b0d80
BF
988 grep -B 1 `git hash-object filename`
989-------------------------------------------------
990
991Figuring out why this works is left as an exercise to the (advanced)
5162e697
DM
992student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and
993linkgit:git-hash-object[1] man pages may prove helpful.
187b0d80 994
aa971cb9 995[[Developing-With-git]]
d19fbc3c
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996Developing with git
997===================
998
e34caace 999[[telling-git-your-name]]
d19fbc3c
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1000Telling git your name
1001---------------------
1002
632cc3e6
TK
1003Before creating any commits, you should introduce yourself to Git.
1004The easiest way to do so is to use linkgit:git-config[1]:
1005
1006------------------------------------------------
1007$ git config --global user.name 'Your Name Comes Here'
1008$ git config --global user.email 'you@yourdomain.example.com'
1009------------------------------------------------
1010
1011Which will add the following to a file named `.gitconfig` in your
1012home directory:
d19fbc3c
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1013
1014------------------------------------------------
d19fbc3c
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1015[user]
1016 name = Your Name Comes Here
1017 email = you@yourdomain.example.com
d19fbc3c
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1018------------------------------------------------
1019
632cc3e6
TK
1020See the "CONFIGURATION FILE" section of linkgit:git-config[1] for
1021details on the configuration file. The file is plain text, so you can
1022also edit it with your favorite editor.
fc90c536 1023
d19fbc3c 1024
e34caace 1025[[creating-a-new-repository]]
d19fbc3c
BF
1026Creating a new repository
1027-------------------------
1028
1029Creating a new repository from scratch is very easy:
1030
1031-------------------------------------------------
1032$ mkdir project
1033$ cd project
f1d2b477 1034$ git init
d19fbc3c
BF
1035-------------------------------------------------
1036
1037If you have some initial content (say, a tarball):
1038
1039-------------------------------------------------
0ddd93b2 1040$ tar xzvf project.tar.gz
d19fbc3c 1041$ cd project
f1d2b477 1042$ git init
d19fbc3c
BF
1043$ git add . # include everything below ./ in the first commit:
1044$ git commit
1045-------------------------------------------------
1046
1047[[how-to-make-a-commit]]
ae25c67a 1048How to make a commit
d19fbc3c
BF
1049--------------------
1050
1051Creating a new commit takes three steps:
1052
1053 1. Making some changes to the working directory using your
1054 favorite editor.
1055 2. Telling git about your changes.
1056 3. Creating the commit using the content you told git about
1057 in step 2.
1058
1059In practice, you can interleave and repeat steps 1 and 2 as many
1060times as you want: in order to keep track of what you want committed
1061at step 3, git maintains a snapshot of the tree's contents in a
1062special staging area called "the index."
1063
01997b4a
BF
1064At the beginning, the content of the index will be identical to
1065that of the HEAD. The command "git diff --cached", which shows
1066the difference between the HEAD and the index, should therefore
1067produce no output at that point.
eb6ae7f4 1068
d19fbc3c
BF
1069Modifying the index is easy:
1070
1071To update the index with the new contents of a modified file, use
1072
1073-------------------------------------------------
1074$ git add path/to/file
1075-------------------------------------------------
1076
1077To add the contents of a new file to the index, use
1078
1079-------------------------------------------------
1080$ git add path/to/file
1081-------------------------------------------------
1082
eb6ae7f4 1083To remove a file from the index and from the working tree,
d19fbc3c
BF
1084
1085-------------------------------------------------
1086$ git rm path/to/file
1087-------------------------------------------------
1088
1089After each step you can verify that
1090
1091-------------------------------------------------
1092$ git diff --cached
1093-------------------------------------------------
1094
1095always shows the difference between the HEAD and the index file--this
1096is what you'd commit if you created the commit now--and that
1097
1098-------------------------------------------------
1099$ git diff
1100-------------------------------------------------
1101
1102shows the difference between the working tree and the index file.
1103
6127c086 1104Note that "git add" always adds just the current contents of a file
d19fbc3c 1105to the index; further changes to the same file will be ignored unless
6127c086 1106you run `git add` on the file again.
d19fbc3c
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1107
1108When you're ready, just run
1109
1110-------------------------------------------------
1111$ git commit
1112-------------------------------------------------
1113
1114and git will prompt you for a commit message and then create the new
3dff5379 1115commit. Check to make sure it looks like what you expected with
d19fbc3c
BF
1116
1117-------------------------------------------------
1118$ git show
1119-------------------------------------------------
1120
1121As a special shortcut,
a6080a0a 1122
d19fbc3c
BF
1123-------------------------------------------------
1124$ git commit -a
1125-------------------------------------------------
1126
1127will update the index with any files that you've modified or removed
1128and create a commit, all in one step.
1129
1130A number of commands are useful for keeping track of what you're
1131about to commit:
1132
1133-------------------------------------------------
1134$ git diff --cached # difference between HEAD and the index; what
1130845b 1135 # would be committed if you ran "commit" now.
d19fbc3c
BF
1136$ git diff # difference between the index file and your
1137 # working directory; changes that would not
1138 # be included if you ran "commit" now.
c64415e2
BF
1139$ git diff HEAD # difference between HEAD and working tree; what
1140 # would be committed if you ran "commit -a" now.
d19fbc3c
BF
1141$ git status # a brief per-file summary of the above.
1142-------------------------------------------------
1143
5162e697 1144You can also use linkgit:git-gui[1] to create commits, view changes in
407c0c87
BF
1145the index and the working tree files, and individually select diff hunks
1146for inclusion in the index (by right-clicking on the diff hunk and
1147choosing "Stage Hunk For Commit").
1148
e34caace 1149[[creating-good-commit-messages]]
ae25c67a 1150Creating good commit messages
d19fbc3c
BF
1151-----------------------------
1152
1153Though not required, it's a good idea to begin the commit message
1154with a single short (less than 50 character) line summarizing the
1155change, followed by a blank line and then a more thorough
52ffe995
JW
1156description. The text up to the first blank line in a commit
1157message is treated as the commit title, and that title is used
1158throughout git. For example, linkgit:git-format-patch[1] turns a
1159commit into email, and it uses the title on the Subject line and the
1160rest of the commit in the body.
1161
d19fbc3c 1162
2dc53617
JH
1163[[ignoring-files]]
1164Ignoring files
1165--------------
1166
1167A project will often generate files that you do 'not' want to track with git.
1168This typically includes files generated by a build process or temporary
1169backup files made by your editor. Of course, 'not' tracking files with git
6127c086 1170is just a matter of 'not' calling `git add` on them. But it quickly becomes
2dc53617 1171annoying to have these untracked files lying around; e.g. they make
dcb11263
CJ
1172`git add .` practically useless, and they keep showing up in the output of
1173`git status`.
2dc53617 1174
464a8a7a
BF
1175You can tell git to ignore certain files by creating a file called .gitignore
1176in the top level of your working directory, with contents such as:
2dc53617
JH
1177
1178-------------------------------------------------
1179# Lines starting with '#' are considered comments.
464a8a7a 1180# Ignore any file named foo.txt.
2dc53617
JH
1181foo.txt
1182# Ignore (generated) html files,
1183*.html
1184# except foo.html which is maintained by hand.
1185!foo.html
1186# Ignore objects and archives.
1187*.[oa]
1188-------------------------------------------------
1189
5162e697 1190See linkgit:gitignore[5] for a detailed explanation of the syntax. You can
464a8a7a
BF
1191also place .gitignore files in other directories in your working tree, and they
1192will apply to those directories and their subdirectories. The `.gitignore`
1193files can be added to your repository like any other files (just run `git add
1194.gitignore` and `git commit`, as usual), which is convenient when the exclude
1195patterns (such as patterns matching build output files) would also make sense
1196for other users who clone your repository.
1197
1198If you wish the exclude patterns to affect only certain repositories
1199(instead of every repository for a given project), you may instead put
1200them in a file in your repository named .git/info/exclude, or in any file
1201specified by the `core.excludesfile` configuration variable. Some git
1202commands can also take exclude patterns directly on the command line.
5162e697 1203See linkgit:gitignore[5] for the details.
2dc53617 1204
e34caace 1205[[how-to-merge]]
ae25c67a 1206How to merge
d19fbc3c
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1207------------
1208
1209You can rejoin two diverging branches of development using
5162e697 1210linkgit:git-merge[1]:
d19fbc3c
BF
1211
1212-------------------------------------------------
1213$ git merge branchname
1214-------------------------------------------------
1215
1216merges the development in the branch "branchname" into the current
e63ec003
MM
1217branch.
1218
1219A merge is made by combining the changes made in "branchname" and the
1220changes made up to the latest commit in your current branch since
1221their histories forked. The work tree is overwritten by the result of
1222the merge when this combining is done cleanly, or overwritten by a
1223half-merged results when this combining results in conflicts.
1224Therefore, if you have uncommitted changes touching the same files as
1225the ones impacted by the merge, Git will refuse to proceed. Most of
1226the time, you will want to commit your changes before you can merge,
1227and if you don't, then linkgit:git-stash[1] can take these changes
1228away while you're doing the merge, and reapply them afterwards.
1229
6a5d0b0a 1230If the changes are independent enough, Git will automatically complete
e63ec003
MM
1231the merge and commit the result (or reuse an existing commit in case
1232of <<fast-forwards,fast-forward>>, see below). On the other hand,
1233if there are conflicts--for example, if the same file is
d19fbc3c
BF
1234modified in two different ways in the remote branch and the local
1235branch--then you are warned; the output may look something like this:
1236
1237-------------------------------------------------
fabbd8f6
BF
1238$ git merge next
1239 100% (4/4) done
1240Auto-merged file.txt
d19fbc3c
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1241CONFLICT (content): Merge conflict in file.txt
1242Automatic merge failed; fix conflicts and then commit the result.
1243-------------------------------------------------
1244
1245Conflict markers are left in the problematic files, and after
1246you resolve the conflicts manually, you can update the index
1247with the contents and run git commit, as you normally would when
1248creating a new file.
1249
1250If you examine the resulting commit using gitk, you will see that it
1251has two parents, one pointing to the top of the current branch, and
1252one to the top of the other branch.
1253
d19fbc3c
BF
1254[[resolving-a-merge]]
1255Resolving a merge
1256-----------------
1257
1258When a merge isn't resolved automatically, git leaves the index and
1259the working tree in a special state that gives you all the
1260information you need to help resolve the merge.
1261
1262Files with conflicts are marked specially in the index, so until you
5162e697 1263resolve the problem and update the index, linkgit:git-commit[1] will
ef561ac7 1264fail:
d19fbc3c
BF
1265
1266-------------------------------------------------
1267$ git commit
1268file.txt: needs merge
1269-------------------------------------------------
1270
5162e697 1271Also, linkgit:git-status[1] will list those files as "unmerged", and the
ef561ac7
BF
1272files with conflicts will have conflict markers added, like this:
1273
1274-------------------------------------------------
1275<<<<<<< HEAD:file.txt
1276Hello world
1277=======
1278Goodbye
1279>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
1280-------------------------------------------------
1281
1282All you need to do is edit the files to resolve the conflicts, and then
1283
1284-------------------------------------------------
1285$ git add file.txt
1286$ git commit
1287-------------------------------------------------
1288
1289Note that the commit message will already be filled in for you with
1290some information about the merge. Normally you can just use this
1291default message unchanged, but you may add additional commentary of
1292your own if desired.
1293
1294The above is all you need to know to resolve a simple merge. But git
1295also provides more information to help resolve conflicts:
1296
e34caace 1297[[conflict-resolution]]
ef561ac7
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1298Getting conflict-resolution help during a merge
1299~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c
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1300
1301All of the changes that git was able to merge automatically are
5162e697 1302already added to the index file, so linkgit:git-diff[1] shows only
ef561ac7 1303the conflicts. It uses an unusual syntax:
d19fbc3c
BF
1304
1305-------------------------------------------------
1306$ git diff
1307diff --cc file.txt
1308index 802992c,2b60207..0000000
1309--- a/file.txt
1310+++ b/file.txt
1311@@@ -1,1 -1,1 +1,5 @@@
1312++<<<<<<< HEAD:file.txt
1313 +Hello world
1314++=======
1315+ Goodbye
1316++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
1317-------------------------------------------------
1318
1130845b 1319Recall that the commit which will be committed after we resolve this
d19fbc3c
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1320conflict will have two parents instead of the usual one: one parent
1321will be HEAD, the tip of the current branch; the other will be the
1322tip of the other branch, which is stored temporarily in MERGE_HEAD.
1323
ef561ac7
BF
1324During the merge, the index holds three versions of each file. Each of
1325these three "file stages" represents a different version of the file:
1326
1327-------------------------------------------------
1328$ git show :1:file.txt # the file in a common ancestor of both branches
4209752d
JH
1329$ git show :2:file.txt # the version from HEAD.
1330$ git show :3:file.txt # the version from MERGE_HEAD.
ef561ac7
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1331-------------------------------------------------
1332
4209752d
JH
1333When you ask linkgit:git-diff[1] to show the conflicts, it runs a
1334three-way diff between the conflicted merge results in the work tree with
1335stages 2 and 3 to show only hunks whose contents come from both sides,
1336mixed (in other words, when a hunk's merge results come only from stage 2,
1337that part is not conflicting and is not shown. Same for stage 3).
ef561ac7
BF
1338
1339The diff above shows the differences between the working-tree version of
1340file.txt and the stage 2 and stage 3 versions. So instead of preceding
1341each line by a single "+" or "-", it now uses two columns: the first
1342column is used for differences between the first parent and the working
1343directory copy, and the second for differences between the second parent
1344and the working directory copy. (See the "COMBINED DIFF FORMAT" section
5162e697 1345of linkgit:git-diff-files[1] for a details of the format.)
ef561ac7
BF
1346
1347After resolving the conflict in the obvious way (but before updating the
1348index), the diff will look like:
d19fbc3c
BF
1349
1350-------------------------------------------------
1351$ git diff
1352diff --cc file.txt
1353index 802992c,2b60207..0000000
1354--- a/file.txt
1355+++ b/file.txt
1356@@@ -1,1 -1,1 +1,1 @@@
1357- Hello world
1358 -Goodbye
1359++Goodbye world
1360-------------------------------------------------
1361
1362This shows that our resolved version deleted "Hello world" from the
1363first parent, deleted "Goodbye" from the second parent, and added
1364"Goodbye world", which was previously absent from both.
1365
ef561ac7
BF
1366Some special diff options allow diffing the working directory against
1367any of these stages:
1368
1369-------------------------------------------------
1370$ git diff -1 file.txt # diff against stage 1
1371$ git diff --base file.txt # same as the above
1372$ git diff -2 file.txt # diff against stage 2
1373$ git diff --ours file.txt # same as the above
1374$ git diff -3 file.txt # diff against stage 3
1375$ git diff --theirs file.txt # same as the above.
1376-------------------------------------------------
1377
0cafe944 1378The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help
ef561ac7 1379for merges:
d19fbc3c
BF
1380
1381-------------------------------------------------
1382$ git log --merge
ef561ac7 1383$ gitk --merge
d19fbc3c
BF
1384-------------------------------------------------
1385
ef561ac7
BF
1386These will display all commits which exist only on HEAD or on
1387MERGE_HEAD, and which touch an unmerged file.
d19fbc3c 1388
5162e697 1389You may also use linkgit:git-mergetool[1], which lets you merge the
c7719fbe 1390unmerged files using external tools such as Emacs or kdiff3.
c64415e2 1391
ef561ac7 1392Each time you resolve the conflicts in a file and update the index:
d19fbc3c
BF
1393
1394-------------------------------------------------
1395$ git add file.txt
d19fbc3c
BF
1396-------------------------------------------------
1397
ef561ac7 1398the different stages of that file will be "collapsed", after which
6127c086 1399`git diff` will (by default) no longer show diffs for that file.
d19fbc3c
BF
1400
1401[[undoing-a-merge]]
ae25c67a 1402Undoing a merge
d19fbc3c
BF
1403---------------
1404
1405If you get stuck and decide to just give up and throw the whole mess
1406away, you can always return to the pre-merge state with
1407
1408-------------------------------------------------
1409$ git reset --hard HEAD
1410-------------------------------------------------
1411
1130845b 1412Or, if you've already committed the merge that you want to throw away,
d19fbc3c
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1413
1414-------------------------------------------------
1c73bb0e 1415$ git reset --hard ORIG_HEAD
d19fbc3c
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1416-------------------------------------------------
1417
1418However, this last command can be dangerous in some cases--never
1419throw away a commit you have already committed if that commit may
1420itself have been merged into another branch, as doing so may confuse
1421further merges.
1422
e34caace 1423[[fast-forwards]]
d19fbc3c
BF
1424Fast-forward merges
1425-------------------
1426
1427There is one special case not mentioned above, which is treated
1428differently. Normally, a merge results in a merge commit, with two
1429parents, one pointing at each of the two lines of development that
1430were merged.
1431
59723040
BF
1432However, if the current branch is a descendant of the other--so every
1433commit present in the one is already contained in the other--then git
a75d7b54 1434just performs a "fast-forward"; the head of the current branch is moved
59723040
BF
1435forward to point at the head of the merged-in branch, without any new
1436commits being created.
d19fbc3c 1437
e34caace 1438[[fixing-mistakes]]
b684f830
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1439Fixing mistakes
1440---------------
1441
1442If you've messed up the working tree, but haven't yet committed your
1443mistake, you can return the entire working tree to the last committed
1444state with
1445
1446-------------------------------------------------
1447$ git reset --hard HEAD
1448-------------------------------------------------
1449
1450If you make a commit that you later wish you hadn't, there are two
1451fundamentally different ways to fix the problem:
1452
1453 1. You can create a new commit that undoes whatever was done
93cbbd71 1454 by the old commit. This is the correct thing if your
b684f830
BF
1455 mistake has already been made public.
1456
1457 2. You can go back and modify the old commit. You should
1458 never do this if you have already made the history public;
1459 git does not normally expect the "history" of a project to
1460 change, and cannot correctly perform repeated merges from
1461 a branch that has had its history changed.
1462
e34caace 1463[[reverting-a-commit]]
b684f830
BF
1464Fixing a mistake with a new commit
1465~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1466
1467Creating a new commit that reverts an earlier change is very easy;
5162e697 1468just pass the linkgit:git-revert[1] command a reference to the bad
b684f830
BF
1469commit; for example, to revert the most recent commit:
1470
1471-------------------------------------------------
1472$ git revert HEAD
1473-------------------------------------------------
1474
1475This will create a new commit which undoes the change in HEAD. You
1476will be given a chance to edit the commit message for the new commit.
1477
1478You can also revert an earlier change, for example, the next-to-last:
1479
1480-------------------------------------------------
1481$ git revert HEAD^
1482-------------------------------------------------
1483
1484In this case git will attempt to undo the old change while leaving
1485intact any changes made since then. If more recent changes overlap
1486with the changes to be reverted, then you will be asked to fix
1487conflicts manually, just as in the case of <<resolving-a-merge,
1488resolving a merge>>.
1489
7cb192ea
BF
1490[[fixing-a-mistake-by-rewriting-history]]
1491Fixing a mistake by rewriting history
b684f830
BF
1492~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1493
1494If the problematic commit is the most recent commit, and you have not
1495yet made that commit public, then you may just
6127c086 1496<<undoing-a-merge,destroy it using `git reset`>>.
b684f830
BF
1497
1498Alternatively, you
1499can edit the working directory and update the index to fix your
1500mistake, just as if you were going to <<how-to-make-a-commit,create a
1501new commit>>, then run
1502
1503-------------------------------------------------
1504$ git commit --amend
1505-------------------------------------------------
1506
1507which will replace the old commit by a new commit incorporating your
1508changes, giving you a chance to edit the old commit message first.
1509
1510Again, you should never do this to a commit that may already have
5162e697 1511been merged into another branch; use linkgit:git-revert[1] instead in
b684f830
BF
1512that case.
1513
7cb192ea 1514It is also possible to replace commits further back in the history, but
b684f830
BF
1515this is an advanced topic to be left for
1516<<cleaning-up-history,another chapter>>.
1517
e34caace 1518[[checkout-of-path]]
b684f830
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1519Checking out an old version of a file
1520~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1521
1522In the process of undoing a previous bad change, you may find it
1523useful to check out an older version of a particular file using
6127c086 1524linkgit:git-checkout[1]. We've used `git checkout` before to switch
b684f830
BF
1525branches, but it has quite different behavior if it is given a path
1526name: the command
1527
1528-------------------------------------------------
1529$ git checkout HEAD^ path/to/file
1530-------------------------------------------------
1531
1532replaces path/to/file by the contents it had in the commit HEAD^, and
1533also updates the index to match. It does not change branches.
1534
1535If you just want to look at an old version of the file, without
1536modifying the working directory, you can do that with
5162e697 1537linkgit:git-show[1]:
b684f830
BF
1538
1539-------------------------------------------------
ed4eb0d8 1540$ git show HEAD^:path/to/file
b684f830
BF
1541-------------------------------------------------
1542
1543which will display the given version of the file.
1544
7a7cc594
JH
1545[[interrupted-work]]
1546Temporarily setting aside work in progress
1547~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1548
1549While you are in the middle of working on something complicated, you
1550find an unrelated but obvious and trivial bug. You would like to fix it
5162e697 1551before continuing. You can use linkgit:git-stash[1] to save the current
7a7cc594
JH
1552state of your work, and after fixing the bug (or, optionally after doing
1553so on a different branch and then coming back), unstash the
1554work-in-progress changes.
1555
1556------------------------------------------------
7a85f6ae 1557$ git stash save "work in progress for foo feature"
7a7cc594
JH
1558------------------------------------------------
1559
1560This command will save your changes away to the `stash`, and
1561reset your working tree and the index to match the tip of your
1562current branch. Then you can make your fix as usual.
1563
1564------------------------------------------------
1565... edit and test ...
1566$ git commit -a -m "blorpl: typofix"
1567------------------------------------------------
1568
1569After that, you can go back to what you were working on with
7b8988e1 1570`git stash pop`:
7a7cc594
JH
1571
1572------------------------------------------------
7b8988e1 1573$ git stash pop
7a7cc594
JH
1574------------------------------------------------
1575
1576
e34caace 1577[[ensuring-good-performance]]
d19fbc3c
BF
1578Ensuring good performance
1579-------------------------
1580
901fd180
TK
1581On large repositories, Git depends on compression to keep the history
1582information from taking up too much space on disk or in memory. Some
1583git commands may automatically run linkgit:git-gc[1], so you don't
1584have to worry about running it manually. However, compressing a large
1585repository may take a while, so you may want to call `gc` explicitly
1586to avoid automatic compression kicking in when it is not convenient.
d19fbc3c 1587
e34caace
BF
1588
1589[[ensuring-reliability]]
11e016a3
BF
1590Ensuring reliability
1591--------------------
1592
e34caace 1593[[checking-for-corruption]]
11e016a3
BF
1594Checking the repository for corruption
1595~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1596
5162e697 1597The linkgit:git-fsck[1] command runs a number of self-consistency checks
1191ee18 1598on the repository, and reports on any problems. This may take some
c6a13b2c 1599time.
21dcb3b7
BF
1600
1601-------------------------------------------------
04e50e94 1602$ git fsck
21dcb3b7
BF
1603dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1604dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1605dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1606dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
1607dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
1608dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
1609dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
1610dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
1611...
1612-------------------------------------------------
1613
c6a13b2c
JH
1614You will see informational messages on dangling objects. They are objects
1615that still exist in the repository but are no longer referenced by any of
1616your branches, and can (and will) be removed after a while with "gc".
b4ab1980 1617You can run `git fsck --no-dangling` to suppress these messages, and still
c6a13b2c 1618view real errors.
1cdade2c 1619
e34caace 1620[[recovering-lost-changes]]
11e016a3
BF
1621Recovering lost changes
1622~~~~~~~~~~~~~~~~~~~~~~~
1623
e34caace 1624[[reflogs]]
559e4d7a
BF
1625Reflogs
1626^^^^^^^
1627
6cf378f0 1628Say you modify a branch with +linkgit:git-reset[1] \--hard+, and then
559e4d7a
BF
1629realize that the branch was the only reference you had to that point in
1630history.
1631
1632Fortunately, git also keeps a log, called a "reflog", of all the
1633previous values of each branch. So in this case you can still find the
a6080a0a 1634old history using, for example,
559e4d7a
BF
1635
1636-------------------------------------------------
1637$ git log master@{1}
1638-------------------------------------------------
1639
e502c2c3
SO
1640This lists the commits reachable from the previous version of the
1641"master" branch head. This syntax can be used with any git command
1642that accepts a commit, not just with git log. Some other examples:
559e4d7a
BF
1643
1644-------------------------------------------------
1645$ git show master@{2} # See where the branch pointed 2,
1646$ git show master@{3} # 3, ... changes ago.
1647$ gitk master@{yesterday} # See where it pointed yesterday,
1648$ gitk master@{"1 week ago"} # ... or last week
953f3d6f
BF
1649$ git log --walk-reflogs master # show reflog entries for master
1650-------------------------------------------------
1651
1652A separate reflog is kept for the HEAD, so
1653
1654-------------------------------------------------
1655$ git show HEAD@{"1 week ago"}
559e4d7a
BF
1656-------------------------------------------------
1657
953f3d6f
BF
1658will show what HEAD pointed to one week ago, not what the current branch
1659pointed to one week ago. This allows you to see the history of what
1660you've checked out.
1661
559e4d7a 1662The reflogs are kept by default for 30 days, after which they may be
5162e697 1663pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn
559e4d7a 1664how to control this pruning, and see the "SPECIFYING REVISIONS"
9d83e382 1665section of linkgit:gitrevisions[7] for details.
559e4d7a
BF
1666
1667Note that the reflog history is very different from normal git history.
1668While normal history is shared by every repository that works on the
1669same project, the reflog history is not shared: it tells you only about
1670how the branches in your local repository have changed over time.
1671
59723040 1672[[dangling-object-recovery]]
559e4d7a
BF
1673Examining dangling objects
1674^^^^^^^^^^^^^^^^^^^^^^^^^^
1675
59723040
BF
1676In some situations the reflog may not be able to save you. For example,
1677suppose you delete a branch, then realize you need the history it
1678contained. The reflog is also deleted; however, if you have not yet
1679pruned the repository, then you may still be able to find the lost
6127c086 1680commits in the dangling objects that `git fsck` reports. See
59723040 1681<<dangling-objects>> for the details.
559e4d7a
BF
1682
1683-------------------------------------------------
1684$ git fsck
1685dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
1686dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
1687dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
1688...
1689-------------------------------------------------
1690
aacd404e 1691You can examine
559e4d7a
BF
1692one of those dangling commits with, for example,
1693
1694------------------------------------------------
1695$ gitk 7281251ddd --not --all
1696------------------------------------------------
1697
1698which does what it sounds like: it says that you want to see the commit
1699history that is described by the dangling commit(s), but not the
1700history that is described by all your existing branches and tags. Thus
1701you get exactly the history reachable from that commit that is lost.
1702(And notice that it might not be just one commit: we only report the
1703"tip of the line" as being dangling, but there might be a whole deep
79c96c57 1704and complex commit history that was dropped.)
559e4d7a
BF
1705
1706If you decide you want the history back, you can always create a new
1707reference pointing to it, for example, a new branch:
1708
1709------------------------------------------------
a6080a0a 1710$ git branch recovered-branch 7281251ddd
559e4d7a
BF
1711------------------------------------------------
1712
59723040
BF
1713Other types of dangling objects (blobs and trees) are also possible, and
1714dangling objects can arise in other situations.
1715
11e016a3 1716
e34caace 1717[[sharing-development]]
d19fbc3c 1718Sharing development with others
b684f830 1719===============================
d19fbc3c 1720
aa971cb9 1721[[getting-updates-With-git-pull]]
6127c086 1722Getting updates with git pull
b684f830 1723-----------------------------
d19fbc3c 1724
e63ec003 1725After you clone a repository and commit a few changes of your own, you
d19fbc3c
BF
1726may wish to check the original repository for updates and merge them
1727into your own work.
1728
aa971cb9 1729We have already seen <<Updating-a-repository-With-git-fetch,how to
0e615b25 1730keep remote-tracking branches up to date>> with linkgit:git-fetch[1],
d19fbc3c
BF
1731and how to merge two branches. So you can merge in changes from the
1732original repository's master branch with:
1733
1734-------------------------------------------------
1735$ git fetch
1736$ git merge origin/master
1737-------------------------------------------------
1738
5162e697 1739However, the linkgit:git-pull[1] command provides a way to do this in
d19fbc3c
BF
1740one step:
1741
1742-------------------------------------------------
1743$ git pull origin master
1744-------------------------------------------------
1745
66a062a1
MM
1746In fact, if you have "master" checked out, then this branch has been
1747configured by "git clone" to get changes from the HEAD branch of the
1748origin repository. So often you can
0eb4f7cd 1749accomplish the above with just a simple
d19fbc3c
BF
1750
1751-------------------------------------------------
1752$ git pull
1753-------------------------------------------------
1754
66a062a1
MM
1755This command will fetch changes from the remote branches to your
1756remote-tracking branches `origin/*`, and merge the default branch into
1757the current branch.
1758
29b9a66f
MM
1759More generally, a branch that is created from a remote-tracking branch
1760will pull
0eb4f7cd
BF
1761by default from that branch. See the descriptions of the
1762branch.<name>.remote and branch.<name>.merge options in
5162e697
DM
1763linkgit:git-config[1], and the discussion of the `--track` option in
1764linkgit:git-checkout[1], to learn how to control these defaults.
d19fbc3c
BF
1765
1766In addition to saving you keystrokes, "git pull" also helps you by
1767producing a default commit message documenting the branch and
1768repository that you pulled from.
1769
1770(But note that no such commit will be created in the case of a
a75d7b54 1771<<fast-forwards,fast-forward>>; instead, your branch will just be
79c96c57 1772updated to point to the latest commit from the upstream branch.)
d19fbc3c 1773
6127c086 1774The `git pull` command can also be given "." as the "remote" repository,
1191ee18 1775in which case it just merges in a branch from the current repository; so
4c63ff45
BF
1776the commands
1777
1778-------------------------------------------------
1779$ git pull . branch
1780$ git merge branch
1781-------------------------------------------------
1782
1783are roughly equivalent. The former is actually very commonly used.
1784
e34caace 1785[[submitting-patches]]
d19fbc3c 1786Submitting patches to a project
b684f830 1787-------------------------------
d19fbc3c
BF
1788
1789If you just have a few changes, the simplest way to submit them may
1790just be to send them as patches in email:
1791
5162e697 1792First, use linkgit:git-format-patch[1]; for example:
d19fbc3c
BF
1793
1794-------------------------------------------------
eb6ae7f4 1795$ git format-patch origin
d19fbc3c
BF
1796-------------------------------------------------
1797
1798will produce a numbered series of files in the current directory, one
1799for each patch in the current branch but not in origin/HEAD.
1800
d84cef18
PO
1801`git format-patch` can include an initial "cover letter". You can insert
1802commentary on individual patches after the three dash line which
1803`format-patch` places after the commit message but before the patch
1804itself. If you use `git notes` to track your cover letter material,
1805`git format-patch --notes` will include the commit's notes in a similar
1806manner.
1807
d19fbc3c
BF
1808You can then import these into your mail client and send them by
1809hand. However, if you have a lot to send at once, you may prefer to
5162e697 1810use the linkgit:git-send-email[1] script to automate the process.
d19fbc3c
BF
1811Consult the mailing list for your project first to determine how they
1812prefer such patches be handled.
1813
e34caace 1814[[importing-patches]]
d19fbc3c 1815Importing patches to a project
b684f830 1816------------------------------
d19fbc3c 1817
5162e697 1818Git also provides a tool called linkgit:git-am[1] (am stands for
d19fbc3c
BF
1819"apply mailbox"), for importing such an emailed series of patches.
1820Just save all of the patch-containing messages, in order, into a
1821single mailbox file, say "patches.mbox", then run
1822
1823-------------------------------------------------
eb6ae7f4 1824$ git am -3 patches.mbox
d19fbc3c
BF
1825-------------------------------------------------
1826
1827Git will apply each patch in order; if any conflicts are found, it
1828will stop, and you can fix the conflicts as described in
01997b4a
BF
1829"<<resolving-a-merge,Resolving a merge>>". (The "-3" option tells
1830git to perform a merge; if you would prefer it just to abort and
1831leave your tree and index untouched, you may omit that option.)
1832
1833Once the index is updated with the results of the conflict
1834resolution, instead of creating a new commit, just run
d19fbc3c
BF
1835
1836-------------------------------------------------
1837$ git am --resolved
1838-------------------------------------------------
1839
1840and git will create the commit for you and continue applying the
1841remaining patches from the mailbox.
1842
1843The final result will be a series of commits, one for each patch in
1844the original mailbox, with authorship and commit log message each
1845taken from the message containing each patch.
1846
eda69449
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1847[[public-repositories]]
1848Public git repositories
1849-----------------------
d19fbc3c 1850
6e30fb0c
DK
1851Another way to submit changes to a project is to tell the maintainer
1852of that project to pull the changes from your repository using
aa971cb9 1853linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull,
6127c086 1854Getting updates with `git pull`>>" we described this as a way to get
6e30fb0c
DK
1855updates from the "main" repository, but it works just as well in the
1856other direction.
d19fbc3c 1857
eda69449
BF
1858If you and the maintainer both have accounts on the same machine, then
1859you can just pull changes from each other's repositories directly;
11d51533 1860commands that accept repository URLs as arguments will also accept a
eda69449 1861local directory name:
d19fbc3c
BF
1862
1863-------------------------------------------------
1864$ git clone /path/to/repository
1865$ git pull /path/to/other/repository
1866-------------------------------------------------
1867
c9016158 1868or an ssh URL:
11d51533
BF
1869
1870-------------------------------------------------
1871$ git clone ssh://yourhost/~you/repository
1872-------------------------------------------------
1873
1874For projects with few developers, or for synchronizing a few private
1875repositories, this may be all you need.
1876
eda69449
BF
1877However, the more common way to do this is to maintain a separate public
1878repository (usually on a different host) for others to pull changes
1879from. This is usually more convenient, and allows you to cleanly
1880separate private work in progress from publicly visible work.
d19fbc3c
BF
1881
1882You will continue to do your day-to-day work in your personal
1883repository, but periodically "push" changes from your personal
1884repository into your public repository, allowing other developers to
1885pull from that repository. So the flow of changes, in a situation
1886where there is one other developer with a public repository, looks
1887like this:
1888
1889 you push
1890 your personal repo ------------------> your public repo
a6080a0a 1891 ^ |
d19fbc3c
BF
1892 | |
1893 | you pull | they pull
1894 | |
1895 | |
1896 | they push V
1897 their public repo <------------------- their repo
1898
11d51533
BF
1899We explain how to do this in the following sections.
1900
eda69449
BF
1901[[setting-up-a-public-repository]]
1902Setting up a public repository
1903~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1904
1905Assume your personal repository is in the directory ~/proj. We
6127c086 1906first create a new clone of the repository and tell `git daemon` that it
eda69449 1907is meant to be public:
d19fbc3c
BF
1908
1909-------------------------------------------------
52c80037 1910$ git clone --bare ~/proj proj.git
eda69449 1911$ touch proj.git/git-daemon-export-ok
d19fbc3c
BF
1912-------------------------------------------------
1913
52c80037 1914The resulting directory proj.git contains a "bare" git repository--it is
eda69449
BF
1915just the contents of the ".git" directory, without any files checked out
1916around it.
d19fbc3c 1917
c64415e2 1918Next, copy proj.git to the server where you plan to host the
d19fbc3c
BF
1919public repository. You can use scp, rsync, or whatever is most
1920convenient.
1921
eda69449
BF
1922[[exporting-via-git]]
1923Exporting a git repository via the git protocol
1924~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1925
1926This is the preferred method.
1927
1928If someone else administers the server, they should tell you what
c9016158 1929directory to put the repository in, and what git:// URL it will appear
eda69449 1930at. You can then skip to the section
d19fbc3c
BF
1931"<<pushing-changes-to-a-public-repository,Pushing changes to a public
1932repository>>", below.
1933
5162e697 1934Otherwise, all you need to do is start linkgit:git-daemon[1]; it will
eda69449
BF
1935listen on port 9418. By default, it will allow access to any directory
1936that looks like a git directory and contains the magic file
6127c086 1937git-daemon-export-ok. Passing some directory paths as `git daemon`
eda69449
BF
1938arguments will further restrict the exports to those paths.
1939
6127c086 1940You can also run `git daemon` as an inetd service; see the
5162e697 1941linkgit:git-daemon[1] man page for details. (See especially the
eda69449 1942examples section.)
d19fbc3c
BF
1943
1944[[exporting-via-http]]
de3f2c7b 1945Exporting a git repository via HTTP
eda69449 1946~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c
BF
1947
1948The git protocol gives better performance and reliability, but on a
de3f2c7b 1949host with a web server set up, HTTP exports may be simpler to set up.
d19fbc3c
BF
1950
1951All you need to do is place the newly created bare git repository in
1952a directory that is exported by the web server, and make some
1953adjustments to give web clients some extra information they need:
1954
1955-------------------------------------------------
1956$ mv proj.git /home/you/public_html/proj.git
1957$ cd proj.git
c64415e2 1958$ git --bare update-server-info
7dce9918 1959$ mv hooks/post-update.sample hooks/post-update
d19fbc3c
BF
1960-------------------------------------------------
1961
1962(For an explanation of the last two lines, see
6998e4db 1963linkgit:git-update-server-info[1] and linkgit:githooks[5].)
d19fbc3c 1964
c9016158
RW
1965Advertise the URL of proj.git. Anybody else should then be able to
1966clone or pull from that URL, for example with a command line like:
d19fbc3c
BF
1967
1968-------------------------------------------------
1969$ git clone http://yourserver.com/~you/proj.git
1970-------------------------------------------------
1971
1972(See also
1973link:howto/setup-git-server-over-http.txt[setup-git-server-over-http]
1974for a slightly more sophisticated setup using WebDAV which also
de3f2c7b 1975allows pushing over HTTP.)
d19fbc3c 1976
d19fbc3c
BF
1977[[pushing-changes-to-a-public-repository]]
1978Pushing changes to a public repository
eda69449 1979~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 1980
eda69449 1981Note that the two techniques outlined above (exporting via
d19fbc3c
BF
1982<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
1983maintainers to fetch your latest changes, but they do not allow write
1984access, which you will need to update the public repository with the
1985latest changes created in your private repository.
1986
5162e697 1987The simplest way to do this is using linkgit:git-push[1] and ssh; to
d19fbc3c
BF
1988update the remote branch named "master" with the latest state of your
1989branch named "master", run
1990
1991-------------------------------------------------
1992$ git push ssh://yourserver.com/~you/proj.git master:master
1993-------------------------------------------------
1994
1995or just
1996
1997-------------------------------------------------
1998$ git push ssh://yourserver.com/~you/proj.git master
1999-------------------------------------------------
2000
6127c086 2001As with `git fetch`, `git push` will complain if this does not result in a
a75d7b54 2002<<fast-forwards,fast-forward>>; see the following section for details on
81eb417a 2003handling this case.
d19fbc3c 2004
11d51533
BF
2005Note that the target of a "push" is normally a
2006<<def_bare_repository,bare>> repository. You can also push to a
2007repository that has a checked-out working tree, but the working tree
2008will not be updated by the push. This may lead to unexpected results if
2009the branch you push to is the currently checked-out branch!
2010
6127c086 2011As with `git fetch`, you may also set up configuration options to
e9b49083
TK
2012save typing; so, for example:
2013
2014-------------------------------------------------
2015$ git remote add public-repo ssh://yourserver.com/~you/proj.git
2016-------------------------------------------------
2017
2018adds the following to `.git/config`:
d19fbc3c
BF
2019
2020-------------------------------------------------
d19fbc3c 2021[remote "public-repo"]
e9b49083
TK
2022 url = yourserver.com:proj.git
2023 fetch = +refs/heads/*:refs/remotes/example/*
d19fbc3c
BF
2024-------------------------------------------------
2025
e9b49083 2026which lets you do the same push with just
d19fbc3c
BF
2027
2028-------------------------------------------------
2029$ git push public-repo master
2030-------------------------------------------------
2031
2032See the explanations of the remote.<name>.url, branch.<name>.remote,
5162e697 2033and remote.<name>.push options in linkgit:git-config[1] for
d19fbc3c
BF
2034details.
2035
81eb417a
BF
2036[[forcing-push]]
2037What to do when a push fails
2038~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2039
a75d7b54 2040If a push would not result in a <<fast-forwards,fast-forward>> of the
81eb417a
BF
2041remote branch, then it will fail with an error like:
2042
2043-------------------------------------------------
2044error: remote 'refs/heads/master' is not an ancestor of
2045 local 'refs/heads/master'.
2046 Maybe you are not up-to-date and need to pull first?
2047error: failed to push to 'ssh://yourserver.com/~you/proj.git'
2048-------------------------------------------------
2049
2050This can happen, for example, if you:
2051
6127c086
FC
2052 - use `git reset --hard` to remove already-published commits, or
2053 - use `git commit --amend` to replace already-published commits
7cb192ea 2054 (as in <<fixing-a-mistake-by-rewriting-history>>), or
6127c086 2055 - use `git rebase` to rebase any already-published commits (as
81eb417a
BF
2056 in <<using-git-rebase>>).
2057
6127c086 2058You may force `git push` to perform the update anyway by preceding the
81eb417a
BF
2059branch name with a plus sign:
2060
2061-------------------------------------------------
2062$ git push ssh://yourserver.com/~you/proj.git +master
2063-------------------------------------------------
2064
d1471e06
TK
2065Note the addition of the `+` sign. Alternatively, you can use the
2066`-f` flag to force the remote update, as in:
2067
2068-------------------------------------------------
2069$ git push -f ssh://yourserver.com/~you/proj.git master
2070-------------------------------------------------
2071
81eb417a 2072Normally whenever a branch head in a public repository is modified, it
9e5d87d4 2073is modified to point to a descendant of the commit that it pointed to
81eb417a 2074before. By forcing a push in this situation, you break that convention.
aa971cb9 2075(See <<problems-With-rewriting-history>>.)
81eb417a
BF
2076
2077Nevertheless, this is a common practice for people that need a simple
2078way to publish a work-in-progress patch series, and it is an acceptable
2079compromise as long as you warn other developers that this is how you
2080intend to manage the branch.
2081
2082It's also possible for a push to fail in this way when other people have
2083the right to push to the same repository. In that case, the correct
843c81dc
EH
2084solution is to retry the push after first updating your work: either by a
2085pull, or by a fetch followed by a rebase; see the
81eb417a 2086<<setting-up-a-shared-repository,next section>> and
6998e4db 2087linkgit:gitcvs-migration[7] for more.
81eb417a 2088
e34caace 2089[[setting-up-a-shared-repository]]
d19fbc3c 2090Setting up a shared repository
eda69449 2091~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c
BF
2092
2093Another way to collaborate is by using a model similar to that
2094commonly used in CVS, where several developers with special rights
2095all push to and pull from a single shared repository. See
6998e4db 2096linkgit:gitcvs-migration[7] for instructions on how to
d19fbc3c
BF
2097set this up.
2098
8fae2225
BF
2099However, while there is nothing wrong with git's support for shared
2100repositories, this mode of operation is not generally recommended,
2101simply because the mode of collaboration that git supports--by
2102exchanging patches and pulling from public repositories--has so many
2103advantages over the central shared repository:
2104
2105 - Git's ability to quickly import and merge patches allows a
2106 single maintainer to process incoming changes even at very
6127c086 2107 high rates. And when that becomes too much, `git pull` provides
8fae2225
BF
2108 an easy way for that maintainer to delegate this job to other
2109 maintainers while still allowing optional review of incoming
2110 changes.
2111 - Since every developer's repository has the same complete copy
2112 of the project history, no repository is special, and it is
2113 trivial for another developer to take over maintenance of a
2114 project, either by mutual agreement, or because a maintainer
2115 becomes unresponsive or difficult to work with.
2116 - The lack of a central group of "committers" means there is
2117 less need for formal decisions about who is "in" and who is
2118 "out".
2119
e34caace 2120[[setting-up-gitweb]]
eda69449
BF
2121Allowing web browsing of a repository
2122~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d19fbc3c 2123
a8cd1402
BF
2124The gitweb cgi script provides users an easy way to browse your
2125project's files and history without having to install git; see the file
04483524 2126gitweb/INSTALL in the git source tree for instructions on setting it up.
d19fbc3c 2127
e34caace 2128[[sharing-development-examples]]
b684f830
BF
2129Examples
2130--------
d19fbc3c 2131
9e2163ea
BF
2132[[maintaining-topic-branches]]
2133Maintaining topic branches for a Linux subsystem maintainer
2134~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2135
2136This describes how Tony Luck uses git in his role as maintainer of the
2137IA64 architecture for the Linux kernel.
2138
2139He uses two public branches:
2140
2141 - A "test" tree into which patches are initially placed so that they
2142 can get some exposure when integrated with other ongoing development.
2143 This tree is available to Andrew for pulling into -mm whenever he
2144 wants.
2145
2146 - A "release" tree into which tested patches are moved for final sanity
2147 checking, and as a vehicle to send them upstream to Linus (by sending
2148 him a "please pull" request.)
2149
2150He also uses a set of temporary branches ("topic branches"), each
2151containing a logical grouping of patches.
2152
2153To set this up, first create your work tree by cloning Linus's public
2154tree:
2155
2156-------------------------------------------------
2157$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git work
2158$ cd work
2159-------------------------------------------------
2160
29b9a66f 2161Linus's tree will be stored in the remote-tracking branch named origin/master,
5162e697
DM
2162and can be updated using linkgit:git-fetch[1]; you can track other
2163public trees using linkgit:git-remote[1] to set up a "remote" and
2164linkgit:git-fetch[1] to keep them up-to-date; see
6e30fb0c 2165<<repositories-and-branches>>.
9e2163ea
BF
2166
2167Now create the branches in which you are going to work; these start out
2168at the current tip of origin/master branch, and should be set up (using
5162e697 2169the --track option to linkgit:git-branch[1]) to merge changes in from
9e2163ea
BF
2170Linus by default.
2171
2172-------------------------------------------------
2173$ git branch --track test origin/master
2174$ git branch --track release origin/master
2175-------------------------------------------------
2176
5162e697 2177These can be easily kept up to date using linkgit:git-pull[1].
9e2163ea
BF
2178
2179-------------------------------------------------
2180$ git checkout test && git pull
2181$ git checkout release && git pull
2182-------------------------------------------------
2183
2184Important note! If you have any local changes in these branches, then
2185this merge will create a commit object in the history (with no local
a75d7b54 2186changes git will simply do a "fast-forward" merge). Many people dislike
9e2163ea
BF
2187the "noise" that this creates in the Linux history, so you should avoid
2188doing this capriciously in the "release" branch, as these noisy commits
2189will become part of the permanent history when you ask Linus to pull
2190from the release branch.
2191
5162e697 2192A few configuration variables (see linkgit:git-config[1]) can
9e2163ea
BF
2193make it easy to push both branches to your public tree. (See
2194<<setting-up-a-public-repository>>.)
2195
2196-------------------------------------------------
2197$ cat >> .git/config <<EOF
2198[remote "mytree"]
2199 url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
2200 push = release
2201 push = test
2202EOF
2203-------------------------------------------------
2204
2205Then you can push both the test and release trees using
5162e697 2206linkgit:git-push[1]:
9e2163ea
BF
2207
2208-------------------------------------------------
2209$ git push mytree
2210-------------------------------------------------
2211
2212or push just one of the test and release branches using:
2213
2214-------------------------------------------------
2215$ git push mytree test
2216-------------------------------------------------
2217
2218or
2219
2220-------------------------------------------------
2221$ git push mytree release
2222-------------------------------------------------
2223
2224Now to apply some patches from the community. Think of a short
2225snappy name for a branch to hold this patch (or related group of
352953a5
TL
2226patches), and create a new branch from a recent stable tag of
2227Linus's branch. Picking a stable base for your branch will:
22281) help you: by avoiding inclusion of unrelated and perhaps lightly
2229tested changes
22302) help future bug hunters that use "git bisect" to find problems
9e2163ea
BF
2231
2232-------------------------------------------------
352953a5 2233$ git checkout -b speed-up-spinlocks v2.6.35
9e2163ea
BF
2234-------------------------------------------------
2235
2236Now you apply the patch(es), run some tests, and commit the change(s). If
2237the patch is a multi-part series, then you should apply each as a separate
2238commit to this branch.
2239
2240-------------------------------------------------
2241$ ... patch ... test ... commit [ ... patch ... test ... commit ]*
2242-------------------------------------------------
2243
2244When you are happy with the state of this change, you can pull it into the
2245"test" branch in preparation to make it public:
2246
2247-------------------------------------------------
2248$ git checkout test && git pull . speed-up-spinlocks
2249-------------------------------------------------
2250
2251It is unlikely that you would have any conflicts here ... but you might if you
2252spent a while on this step and had also pulled new versions from upstream.
2253
2254Some time later when enough time has passed and testing done, you can pull the
2255same branch into the "release" tree ready to go upstream. This is where you
2256see the value of keeping each patch (or patch series) in its own branch. It
2257means that the patches can be moved into the "release" tree in any order.
2258
2259-------------------------------------------------
2260$ git checkout release && git pull . speed-up-spinlocks
2261-------------------------------------------------
2262
2263After a while, you will have a number of branches, and despite the
2264well chosen names you picked for each of them, you may forget what
2265they are for, or what status they are in. To get a reminder of what
2266changes are in a specific branch, use:
2267
2268-------------------------------------------------
467c0197 2269$ git log linux..branchname | git shortlog
9e2163ea
BF
2270-------------------------------------------------
2271
06ada152 2272To see whether it has already been merged into the test or release branches,
9e2163ea
BF
2273use:
2274
2275-------------------------------------------------
2276$ git log test..branchname
2277-------------------------------------------------
2278
2279or
2280
2281-------------------------------------------------
2282$ git log release..branchname
2283-------------------------------------------------
2284
06ada152 2285(If this branch has not yet been merged, you will see some log entries.
9e2163ea
BF
2286If it has been merged, then there will be no output.)
2287
2288Once a patch completes the great cycle (moving from test to release,
2289then pulled by Linus, and finally coming back into your local
06ada152 2290"origin/master" branch), the branch for this change is no longer needed.
9e2163ea
BF
2291You detect this when the output from:
2292
2293-------------------------------------------------
2294$ git log origin..branchname
2295-------------------------------------------------
2296
2297is empty. At this point the branch can be deleted:
2298
2299-------------------------------------------------
2300$ git branch -d branchname
2301-------------------------------------------------
2302
2303Some changes are so trivial that it is not necessary to create a separate
2304branch and then merge into each of the test and release branches. For
2305these changes, just apply directly to the "release" branch, and then
2306merge that into the "test" branch.
2307
2308To create diffstat and shortlog summaries of changes to include in a "please
2309pull" request to Linus you can use:
2310
2311-------------------------------------------------
2312$ git diff --stat origin..release
2313-------------------------------------------------
2314
2315and
2316
2317-------------------------------------------------
2318$ git log -p origin..release | git shortlog
2319-------------------------------------------------
2320
2321Here are some of the scripts that simplify all this even further.
2322
2323-------------------------------------------------
2324==== update script ====
2325# Update a branch in my GIT tree. If the branch to be updated
2326# is origin, then pull from kernel.org. Otherwise merge
2327# origin/master branch into test|release branch
2328
2329case "$1" in
2330test|release)
2331 git checkout $1 && git pull . origin
2332 ;;
2333origin)
fc74ecc1 2334 before=$(git rev-parse refs/remotes/origin/master)
9e2163ea 2335 git fetch origin
fc74ecc1 2336 after=$(git rev-parse refs/remotes/origin/master)
9e2163ea
BF
2337 if [ $before != $after ]
2338 then
2339 git log $before..$after | git shortlog
2340 fi
2341 ;;
2342*)
2343 echo "Usage: $0 origin|test|release" 1>&2
2344 exit 1
2345 ;;
2346esac
2347-------------------------------------------------
2348
2349-------------------------------------------------
2350==== merge script ====
2351# Merge a branch into either the test or release branch
2352
2353pname=$0
2354
2355usage()
2356{
2357 echo "Usage: $pname branch test|release" 1>&2
2358 exit 1
2359}
2360
fc74ecc1 2361git show-ref -q --verify -- refs/heads/"$1" || {
9e2163ea
BF
2362 echo "Can't see branch <$1>" 1>&2
2363 usage
fc74ecc1 2364}
9e2163ea
BF
2365
2366case "$2" in
2367test|release)
2368 if [ $(git log $2..$1 | wc -c) -eq 0 ]
2369 then
2370 echo $1 already merged into $2 1>&2
2371 exit 1
2372 fi
2373 git checkout $2 && git pull . $1
2374 ;;
2375*)
2376 usage
2377 ;;
2378esac
2379-------------------------------------------------
2380
2381-------------------------------------------------
2382==== status script ====
2383# report on status of my ia64 GIT tree
2384
2385gb=$(tput setab 2)
2386rb=$(tput setab 1)
2387restore=$(tput setab 9)
2388
2389if [ `git rev-list test..release | wc -c` -gt 0 ]
2390then
2391 echo $rb Warning: commits in release that are not in test $restore
2392 git log test..release
2393fi
2394
fc74ecc1 2395for branch in `git show-ref --heads | sed 's|^.*/||'`
9e2163ea
BF
2396do
2397 if [ $branch = test -o $branch = release ]
2398 then
2399 continue
2400 fi
2401
2402 echo -n $gb ======= $branch ====== $restore " "
2403 status=
2404 for ref in test release origin/master
2405 do
2406 if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
2407 then
2408 status=$status${ref:0:1}
2409 fi
2410 done
2411 case $status in
2412 trl)
2413 echo $rb Need to pull into test $restore
2414 ;;
2415 rl)
2416 echo "In test"
2417 ;;
2418 l)
2419 echo "Waiting for linus"
2420 ;;
2421 "")
2422 echo $rb All done $restore
2423 ;;
2424 *)
2425 echo $rb "<$status>" $restore
2426 ;;
2427 esac
2428 git log origin/master..$branch | git shortlog
2429done
2430-------------------------------------------------
d19fbc3c 2431
d19fbc3c 2432
d19fbc3c 2433[[cleaning-up-history]]
4c63ff45
BF
2434Rewriting history and maintaining patch series
2435==============================================
2436
2437Normally commits are only added to a project, never taken away or
2438replaced. Git is designed with this assumption, and violating it will
2439cause git's merge machinery (for example) to do the wrong thing.
2440
2441However, there is a situation in which it can be useful to violate this
2442assumption.
2443
e34caace 2444[[patch-series]]
4c63ff45
BF
2445Creating the perfect patch series
2446---------------------------------
2447
2448Suppose you are a contributor to a large project, and you want to add a
2449complicated feature, and to present it to the other developers in a way
2450that makes it easy for them to read your changes, verify that they are
2451correct, and understand why you made each change.
2452
b181d57f 2453If you present all of your changes as a single patch (or commit), they
79c96c57 2454may find that it is too much to digest all at once.
4c63ff45
BF
2455
2456If you present them with the entire history of your work, complete with
2457mistakes, corrections, and dead ends, they may be overwhelmed.
2458
2459So the ideal is usually to produce a series of patches such that:
2460
2461 1. Each patch can be applied in order.
2462
2463 2. Each patch includes a single logical change, together with a
2464 message explaining the change.
2465
2466 3. No patch introduces a regression: after applying any initial
2467 part of the series, the resulting project still compiles and
2468 works, and has no bugs that it didn't have before.
2469
2470 4. The complete series produces the same end result as your own
2471 (probably much messier!) development process did.
2472
b181d57f
BF
2473We will introduce some tools that can help you do this, explain how to
2474use them, and then explain some of the problems that can arise because
2475you are rewriting history.
4c63ff45 2476
e34caace 2477[[using-git-rebase]]
6127c086 2478Keeping a patch series up to date using git rebase
4c63ff45
BF
2479--------------------------------------------------
2480
79c96c57
MC
2481Suppose that you create a branch "mywork" on a remote-tracking branch
2482"origin", and create some commits on top of it:
4c63ff45
BF
2483
2484-------------------------------------------------
2485$ git checkout -b mywork origin
2486$ vi file.txt
2487$ git commit
2488$ vi otherfile.txt
2489$ git commit
2490...
2491-------------------------------------------------
2492
2493You have performed no merges into mywork, so it is just a simple linear
2494sequence of patches on top of "origin":
2495
1dc71a91 2496................................................
fa8347b8 2497 o--o--O <-- origin
4c63ff45 2498 \
fa8347b8 2499 a--b--c <-- mywork
1dc71a91 2500................................................
4c63ff45
BF
2501
2502Some more interesting work has been done in the upstream project, and
2503"origin" has advanced:
2504
1dc71a91 2505................................................
4c63ff45
BF
2506 o--o--O--o--o--o <-- origin
2507 \
2508 a--b--c <-- mywork
1dc71a91 2509................................................
4c63ff45
BF
2510
2511At this point, you could use "pull" to merge your changes back in;
2512the result would create a new merge commit, like this:
2513
1dc71a91 2514................................................
4c63ff45
BF
2515 o--o--O--o--o--o <-- origin
2516 \ \
2517 a--b--c--m <-- mywork
1dc71a91 2518................................................
a6080a0a 2519
4c63ff45
BF
2520However, if you prefer to keep the history in mywork a simple series of
2521commits without any merges, you may instead choose to use
5162e697 2522linkgit:git-rebase[1]:
4c63ff45
BF
2523
2524-------------------------------------------------
2525$ git checkout mywork
2526$ git rebase origin
2527-------------------------------------------------
2528
b181d57f 2529This will remove each of your commits from mywork, temporarily saving
51ef1daa 2530them as patches (in a directory named ".git/rebase-apply"), update mywork to
b181d57f
BF
2531point at the latest version of origin, then apply each of the saved
2532patches to the new mywork. The result will look like:
4c63ff45
BF
2533
2534
1dc71a91 2535................................................
4c63ff45
BF
2536 o--o--O--o--o--o <-- origin
2537 \
2538 a'--b'--c' <-- mywork
1dc71a91 2539................................................
4c63ff45 2540
b181d57f 2541In the process, it may discover conflicts. In that case it will stop
6127c086 2542and allow you to fix the conflicts; after fixing conflicts, use `git add`
7a7d4ef6 2543to update the index with those contents, and then, instead of
6127c086 2544running `git commit`, just run
4c63ff45
BF
2545
2546-------------------------------------------------
2547$ git rebase --continue
2548-------------------------------------------------
2549
2550and git will continue applying the rest of the patches.
2551
b6cbca38 2552At any point you may use the `--abort` option to abort this process and
4c63ff45
BF
2553return mywork to the state it had before you started the rebase:
2554
2555-------------------------------------------------
2556$ git rebase --abort
2557-------------------------------------------------
2558
7cb192ea
BF
2559[[rewriting-one-commit]]
2560Rewriting a single commit
365aa199
BF
2561-------------------------
2562
7cb192ea 2563We saw in <<fixing-a-mistake-by-rewriting-history>> that you can replace the
365aa199
BF
2564most recent commit using
2565
2566-------------------------------------------------
2567$ git commit --amend
2568-------------------------------------------------
2569
2570which will replace the old commit by a new commit incorporating your
2571changes, giving you a chance to edit the old commit message first.
2572
5162e697 2573You can also use a combination of this and linkgit:git-rebase[1] to
7cb192ea
BF
2574replace a commit further back in your history and recreate the
2575intervening changes on top of it. First, tag the problematic commit
2576with
365aa199
BF
2577
2578-------------------------------------------------
2579$ git tag bad mywork~5
2580-------------------------------------------------
2581
6127c086 2582(Either gitk or `git log` may be useful for finding the commit.)
365aa199 2583
25d9f3fa
BF
2584Then check out that commit, edit it, and rebase the rest of the series
2585on top of it (note that we could check out the commit on a temporary
2586branch, but instead we're using a <<detached-head,detached head>>):
365aa199
BF
2587
2588-------------------------------------------------
25d9f3fa 2589$ git checkout bad
365aa199
BF
2590$ # make changes here and update the index
2591$ git commit --amend
25d9f3fa 2592$ git rebase --onto HEAD bad mywork
365aa199
BF
2593-------------------------------------------------
2594
25d9f3fa
BF
2595When you're done, you'll be left with mywork checked out, with the top
2596patches on mywork reapplied on top of your modified commit. You can
365aa199
BF
2597then clean up with
2598
2599-------------------------------------------------
365aa199
BF
2600$ git tag -d bad
2601-------------------------------------------------
2602
2603Note that the immutable nature of git history means that you haven't really
2604"modified" existing commits; instead, you have replaced the old commits with
2605new commits having new object names.
2606
e34caace 2607[[reordering-patch-series]]
4c63ff45
BF
2608Reordering or selecting from a patch series
2609-------------------------------------------
2610
5162e697 2611Given one existing commit, the linkgit:git-cherry-pick[1] command
b181d57f
BF
2612allows you to apply the change introduced by that commit and create a
2613new commit that records it. So, for example, if "mywork" points to a
2614series of patches on top of "origin", you might do something like:
2615
2616-------------------------------------------------
2617$ git checkout -b mywork-new origin
2618$ gitk origin..mywork &
2619-------------------------------------------------
2620
06ada152 2621and browse through the list of patches in the mywork branch using gitk,
b181d57f 2622applying them (possibly in a different order) to mywork-new using
6127c086 2623cherry-pick, and possibly modifying them as you go using `git commit --amend`.
5162e697 2624The linkgit:git-gui[1] command may also help as it allows you to
6e30fb0c
DK
2625individually select diff hunks for inclusion in the index (by
2626right-clicking on the diff hunk and choosing "Stage Hunk for Commit").
b181d57f 2627
6127c086 2628Another technique is to use `git format-patch` to create a series of
b181d57f 2629patches, then reset the state to before the patches:
4c63ff45 2630
b181d57f
BF
2631-------------------------------------------------
2632$ git format-patch origin
2633$ git reset --hard origin
2634-------------------------------------------------
4c63ff45 2635
b181d57f 2636Then modify, reorder, or eliminate patches as preferred before applying
5162e697 2637them again with linkgit:git-am[1].
4c63ff45 2638
e34caace 2639[[patch-series-tools]]
4c63ff45
BF
2640Other tools
2641-----------
2642
73a1d050 2643There are numerous other tools, such as StGit, which exist for the
79c96c57 2644purpose of maintaining a patch series. These are outside of the scope of
b181d57f 2645this manual.
4c63ff45 2646
aa971cb9 2647[[problems-With-rewriting-history]]
4c63ff45
BF
2648Problems with rewriting history
2649-------------------------------
2650
b181d57f
BF
2651The primary problem with rewriting the history of a branch has to do
2652with merging. Suppose somebody fetches your branch and merges it into
2653their branch, with a result something like this:
2654
1dc71a91 2655................................................
b181d57f
BF
2656 o--o--O--o--o--o <-- origin
2657 \ \
2658 t--t--t--m <-- their branch:
1dc71a91 2659................................................
b181d57f
BF
2660
2661Then suppose you modify the last three commits:
2662
1dc71a91 2663................................................
b181d57f
BF
2664 o--o--o <-- new head of origin
2665 /
2666 o--o--O--o--o--o <-- old head of origin
1dc71a91 2667................................................
b181d57f
BF
2668
2669If we examined all this history together in one repository, it will
2670look like:
2671
1dc71a91 2672................................................
b181d57f
BF
2673 o--o--o <-- new head of origin
2674 /
2675 o--o--O--o--o--o <-- old head of origin
2676 \ \
2677 t--t--t--m <-- their branch:
1dc71a91 2678................................................
b181d57f
BF
2679
2680Git has no way of knowing that the new head is an updated version of
2681the old head; it treats this situation exactly the same as it would if
2682two developers had independently done the work on the old and new heads
2683in parallel. At this point, if someone attempts to merge the new head
2684in to their branch, git will attempt to merge together the two (old and
2685new) lines of development, instead of trying to replace the old by the
2686new. The results are likely to be unexpected.
2687
2688You may still choose to publish branches whose history is rewritten,
2689and it may be useful for others to be able to fetch those branches in
2690order to examine or test them, but they should not attempt to pull such
2691branches into their own work.
2692
2693For true distributed development that supports proper merging,
2694published branches should never be rewritten.
2695
3fb00282
SP
2696[[bisect-merges]]
2697Why bisecting merge commits can be harder than bisecting linear history
2698-----------------------------------------------------------------------
2699
5162e697 2700The linkgit:git-bisect[1] command correctly handles history that
3fb00282
SP
2701includes merge commits. However, when the commit that it finds is a
2702merge commit, the user may need to work harder than usual to figure out
2703why that commit introduced a problem.
2704
2705Imagine this history:
2706
2707................................................
2708 ---Z---o---X---...---o---A---C---D
2709 \ /
2710 o---o---Y---...---o---B
2711................................................
2712
2713Suppose that on the upper line of development, the meaning of one
2714of the functions that exists at Z is changed at commit X. The
2715commits from Z leading to A change both the function's
2716implementation and all calling sites that exist at Z, as well
2717as new calling sites they add, to be consistent. There is no
2718bug at A.
2719
2720Suppose that in the meantime on the lower line of development somebody
2721adds a new calling site for that function at commit Y. The
2722commits from Z leading to B all assume the old semantics of that
2723function and the callers and the callee are consistent with each
2724other. There is no bug at B, either.
2725
2726Suppose further that the two development lines merge cleanly at C,
2727so no conflict resolution is required.
2728
2729Nevertheless, the code at C is broken, because the callers added
2730on the lower line of development have not been converted to the new
2731semantics introduced on the upper line of development. So if all
2732you know is that D is bad, that Z is good, and that
5162e697 2733linkgit:git-bisect[1] identifies C as the culprit, how will you
3fb00282
SP
2734figure out that the problem is due to this change in semantics?
2735
6127c086 2736When the result of a `git bisect` is a non-merge commit, you should
3fb00282
SP
2737normally be able to discover the problem by examining just that commit.
2738Developers can make this easy by breaking their changes into small
2739self-contained commits. That won't help in the case above, however,
2740because the problem isn't obvious from examination of any single
2741commit; instead, a global view of the development is required. To
2742make matters worse, the change in semantics in the problematic
2743function may be just one small part of the changes in the upper
2744line of development.
2745
2746On the other hand, if instead of merging at C you had rebased the
2747history between Z to B on top of A, you would have gotten this
2748linear history:
2749
2750................................................................
2751 ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*
2752................................................................
2753
2754Bisecting between Z and D* would hit a single culprit commit Y*,
2755and understanding why Y* was broken would probably be easier.
2756
2757Partly for this reason, many experienced git users, even when
2758working on an otherwise merge-heavy project, keep the history
2759linear by rebasing against the latest upstream version before
2760publishing.
2761
e34caace 2762[[advanced-branch-management]]
b181d57f
BF
2763Advanced branch management
2764==========================
4c63ff45 2765
e34caace 2766[[fetching-individual-branches]]
b181d57f
BF
2767Fetching individual branches
2768----------------------------
2769
5162e697 2770Instead of using linkgit:git-remote[1], you can also choose just
b181d57f
BF
2771to update one branch at a time, and to store it locally under an
2772arbitrary name:
2773
2774-------------------------------------------------
2775$ git fetch origin todo:my-todo-work
2776-------------------------------------------------
2777
2778The first argument, "origin", just tells git to fetch from the
2779repository you originally cloned from. The second argument tells git
2780to fetch the branch named "todo" from the remote repository, and to
2781store it locally under the name refs/heads/my-todo-work.
2782
2783You can also fetch branches from other repositories; so
2784
2785-------------------------------------------------
2786$ git fetch git://example.com/proj.git master:example-master
2787-------------------------------------------------
2788
2789will create a new branch named "example-master" and store in it the
2790branch named "master" from the repository at the given URL. If you
2791already have a branch named example-master, it will attempt to
59723040
BF
2792<<fast-forwards,fast-forward>> to the commit given by example.com's
2793master branch. In more detail:
b181d57f 2794
59723040
BF
2795[[fetch-fast-forwards]]
2796git fetch and fast-forwards
2797---------------------------
b181d57f 2798
6127c086 2799In the previous example, when updating an existing branch, "git fetch"
7a7d4ef6 2800checks to make sure that the most recent commit on the remote
b181d57f
BF
2801branch is a descendant of the most recent commit on your copy of the
2802branch before updating your copy of the branch to point at the new
a75d7b54 2803commit. Git calls this process a <<fast-forwards,fast-forward>>.
b181d57f 2804
a75d7b54 2805A fast-forward looks something like this:
b181d57f 2806
1dc71a91 2807................................................
b181d57f
BF
2808 o--o--o--o <-- old head of the branch
2809 \
2810 o--o--o <-- new head of the branch
1dc71a91 2811................................................
b181d57f
BF
2812
2813
2814In some cases it is possible that the new head will *not* actually be
2815a descendant of the old head. For example, the developer may have
2816realized she made a serious mistake, and decided to backtrack,
2817resulting in a situation like:
2818
1dc71a91 2819................................................
b181d57f
BF
2820 o--o--o--o--a--b <-- old head of the branch
2821 \
2822 o--o--o <-- new head of the branch
1dc71a91 2823................................................
b181d57f 2824
6127c086 2825In this case, "git fetch" will fail, and print out a warning.
b181d57f
BF
2826
2827In that case, you can still force git to update to the new head, as
2828described in the following section. However, note that in the
2829situation above this may mean losing the commits labeled "a" and "b",
2830unless you've already created a reference of your own pointing to
2831them.
2832
e34caace 2833[[forcing-fetch]]
6127c086 2834Forcing git fetch to do non-fast-forward updates
b181d57f
BF
2835------------------------------------------------
2836
2837If git fetch fails because the new head of a branch is not a
2838descendant of the old head, you may force the update with:
2839
2840-------------------------------------------------
2841$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
2842-------------------------------------------------
2843
c64415e2
BF
2844Note the addition of the "+" sign. Alternatively, you can use the "-f"
2845flag to force updates of all the fetched branches, as in:
2846
2847-------------------------------------------------
2848$ git fetch -f origin
2849-------------------------------------------------
2850
2851Be aware that commits that the old version of example/master pointed at
2852may be lost, as we saw in the previous section.
b181d57f 2853
e34caace 2854[[remote-branch-configuration]]
29b9a66f
MM
2855Configuring remote-tracking branches
2856------------------------------------
b181d57f
BF
2857
2858We saw above that "origin" is just a shortcut to refer to the
79c96c57 2859repository that you originally cloned from. This information is
b181d57f 2860stored in git configuration variables, which you can see using
5162e697 2861linkgit:git-config[1]:
b181d57f
BF
2862
2863-------------------------------------------------
9d13bda3 2864$ git config -l
b181d57f
BF
2865core.repositoryformatversion=0
2866core.filemode=true
2867core.logallrefupdates=true
2868remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
2869remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
2870branch.master.remote=origin
2871branch.master.merge=refs/heads/master
2872-------------------------------------------------
2873
2874If there are other repositories that you also use frequently, you can
2875create similar configuration options to save typing; for example,
b181d57f
BF
2876
2877-------------------------------------------------
47adb8ac 2878$ git remote add example git://example.com/proj.git
b181d57f
BF
2879-------------------------------------------------
2880
47adb8ac 2881adds the following to `.git/config`:
b181d57f
BF
2882
2883-------------------------------------------------
47adb8ac
TK
2884[remote "example"]
2885 url = git://example.com/proj.git
2886 fetch = +refs/heads/*:refs/remotes/example/*
b181d57f
BF
2887-------------------------------------------------
2888
47adb8ac
TK
2889Also note that the above configuration can be performed by directly
2890editing the file `.git/config` instead of using linkgit:git-remote[1].
b181d57f 2891
47adb8ac
TK
2892After configuring the remote, the following three commands will do the
2893same thing:
b181d57f
BF
2894
2895-------------------------------------------------
47adb8ac
TK
2896$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/*
2897$ git fetch example +refs/heads/*:refs/remotes/example/*
b181d57f
BF
2898$ git fetch example
2899-------------------------------------------------
2900
5162e697 2901See linkgit:git-config[1] for more details on the configuration
47adb8ac
TK
2902options mentioned above and linkgit:git-fetch[1] for more details on
2903the refspec syntax.
d19fbc3c 2904
d19fbc3c 2905
036f8199
BF
2906[[git-concepts]]
2907Git concepts
2908============
d19fbc3c 2909
036f8199
BF
2910Git is built on a small number of simple but powerful ideas. While it
2911is possible to get things done without understanding them, you will find
2912git much more intuitive if you do.
2913
2914We start with the most important, the <<def_object_database,object
2915database>> and the <<def_index,index>>.
b181d57f 2916
e34caace 2917[[the-object-database]]
b181d57f
BF
2918The Object Database
2919-------------------
2920
1bbf1c79
BF
2921
2922We already saw in <<understanding-commits>> that all commits are stored
2923under a 40-digit "object name". In fact, all the information needed to
2924represent the history of a project is stored in objects with such names.
a6e5ef7d
FC
2925In each case the name is calculated by taking the SHA-1 hash of the
2926contents of the object. The SHA-1 hash is a cryptographic hash function.
1bbf1c79
BF
2927What that means to us is that it is impossible to find two different
2928objects with the same name. This has a number of advantages; among
2929others:
2930
2931- Git can quickly determine whether two objects are identical or not,
2932 just by comparing names.
06ada152 2933- Since object names are computed the same way in every repository, the
1bbf1c79
BF
2934 same content stored in two repositories will always be stored under
2935 the same name.
2936- Git can detect errors when it reads an object, by checking that the
a6e5ef7d 2937 object's name is still the SHA-1 hash of its contents.
1bbf1c79
BF
2938
2939(See <<object-details>> for the details of the object formatting and
a6e5ef7d 2940SHA-1 calculation.)
1bbf1c79
BF
2941
2942There are four different types of objects: "blob", "tree", "commit", and
2943"tag".
2944
2945- A <<def_blob_object,"blob" object>> is used to store file data.
843c81dc 2946- A <<def_tree_object,"tree" object>> ties one or more
1bbf1c79
BF
2947 "blob" objects into a directory structure. In addition, a tree object
2948 can refer to other tree objects, thus creating a directory hierarchy.
2949- A <<def_commit_object,"commit" object>> ties such directory hierarchies
2ef8ac1b 2950 together into a <<def_DAG,directed acyclic graph>> of revisions--each
1bbf1c79
BF
2951 commit contains the object name of exactly one tree designating the
2952 directory hierarchy at the time of the commit. In addition, a commit
2953 refers to "parent" commit objects that describe the history of how we
2954 arrived at that directory hierarchy.
2955- A <<def_tag_object,"tag" object>> symbolically identifies and can be
2956 used to sign other objects. It contains the object name and type of
2957 another object, a symbolic name (of course!) and, optionally, a
2958 signature.
b181d57f 2959
b181d57f
BF
2960The object types in some more detail:
2961
513d419c
BF
2962[[commit-object]]
2963Commit Object
2964~~~~~~~~~~~~~
b181d57f 2965
1bbf1c79
BF
2966The "commit" object links a physical state of a tree with a description
2967of how we got there and why. Use the --pretty=raw option to
5162e697 2968linkgit:git-show[1] or linkgit:git-log[1] to examine your favorite
1bbf1c79
BF
2969commit:
2970
2971------------------------------------------------
2972$ git show -s --pretty=raw 2be7fcb476
2973commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
2974tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
2975parent 257a84d9d02e90447b149af58b271c19405edb6a
2976author Dave Watson <dwatson@mimvista.com> 1187576872 -0400
2977committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700
2978
2979 Fix misspelling of 'suppress' in docs
2980
2981 Signed-off-by: Junio C Hamano <gitster@pobox.com>
2982------------------------------------------------
2983
2984As you can see, a commit is defined by:
2985
a6e5ef7d 2986- a tree: The SHA-1 name of a tree object (as defined below), representing
1bbf1c79 2987 the contents of a directory at a certain point in time.
edfbbf7e 2988- parent(s): The SHA-1 name(s) of some number of commits which represent the
9e5d87d4 2989 immediately previous step(s) in the history of the project. The
1bbf1c79
BF
2990 example above has one parent; merge commits may have more than
2991 one. A commit with no parents is called a "root" commit, and
2992 represents the initial revision of a project. Each project must have
2993 at least one root. A project can also have multiple roots, though
2994 that isn't common (or necessarily a good idea).
2995- an author: The name of the person responsible for this change, together
2996 with its date.
2997- a committer: The name of the person who actually created the commit,
2998 with the date it was done. This may be different from the author, for
2999 example, if the author was someone who wrote a patch and emailed it
3000 to the person who used it to create the commit.
3001- a comment describing this commit.
3002
3003Note that a commit does not itself contain any information about what
3004actually changed; all changes are calculated by comparing the contents
3005of the tree referred to by this commit with the trees associated with
3006its parents. In particular, git does not attempt to record file renames
3007explicitly, though it can identify cases where the existence of the same
3008file data at changing paths suggests a rename. (See, for example, the
5162e697 3009-M option to linkgit:git-diff[1]).
1bbf1c79 3010
5162e697 3011A commit is usually created by linkgit:git-commit[1], which creates a
1bbf1c79
BF
3012commit whose parent is normally the current HEAD, and whose tree is
3013taken from the content currently stored in the index.
b181d57f 3014
e34caace 3015[[tree-object]]
b181d57f 3016Tree Object
971aa71f 3017~~~~~~~~~~~
b181d57f 3018
5162e697
DM
3019The ever-versatile linkgit:git-show[1] command can also be used to
3020examine tree objects, but linkgit:git-ls-tree[1] will give you more
1bbf1c79
BF
3021details:
3022
3023------------------------------------------------
3024$ git ls-tree fb3a8bdd0ce
3025100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
3026100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
3027100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
3028040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
3029100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
3030100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
3031100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
3032100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
3033...
3034------------------------------------------------
3035
3036As you can see, a tree object contains a list of entries, each with a
a6e5ef7d 3037mode, object type, SHA-1 name, and name, sorted by name. It represents
1bbf1c79
BF
3038the contents of a single directory tree.
3039
3040The object type may be a blob, representing the contents of a file, or
3041another tree, representing the contents of a subdirectory. Since trees
a6e5ef7d
FC
3042and blobs, like all other objects, are named by the SHA-1 hash of their
3043contents, two trees have the same SHA-1 name if and only if their
1bbf1c79
BF
3044contents (including, recursively, the contents of all subdirectories)
3045are identical. This allows git to quickly determine the differences
3046between two related tree objects, since it can ignore any entries with
3047identical object names.
3048
3049(Note: in the presence of submodules, trees may also have commits as
6dd14366 3050entries. See <<submodules>> for documentation.)
1bbf1c79
BF
3051
3052Note that the files all have mode 644 or 755: git actually only pays
3053attention to the executable bit.
b181d57f 3054
513d419c
BF
3055[[blob-object]]
3056Blob Object
3057~~~~~~~~~~~
b181d57f 3058
5162e697 3059You can use linkgit:git-show[1] to examine the contents of a blob; take,
1bbf1c79 3060for example, the blob in the entry for "COPYING" from the tree above:
b181d57f 3061
1bbf1c79
BF
3062------------------------------------------------
3063$ git show 6ff87c4664
3064
3065 Note that the only valid version of the GPL as far as this project
3066 is concerned is _this_ particular version of the license (ie v2, not
3067 v2.2 or v3.x or whatever), unless explicitly otherwise stated.
3068...
3069------------------------------------------------
b181d57f 3070
1bbf1c79
BF
3071A "blob" object is nothing but a binary blob of data. It doesn't refer
3072to anything else or have attributes of any kind.
3073
3074Since the blob is entirely defined by its data, if two files in a
3075directory tree (or in multiple different versions of the repository)
3076have the same contents, they will share the same blob object. The object
3077is totally independent of its location in the directory tree, and
3078renaming a file does not change the object that file is associated with.
3079
3080Note that any tree or blob object can be examined using
5162e697 3081linkgit:git-show[1] with the <revision>:<path> syntax. This can
1bbf1c79
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3082sometimes be useful for browsing the contents of a tree that is not
3083currently checked out.
b181d57f 3084
e34caace 3085[[trust]]
b181d57f 3086Trust
971aa71f 3087~~~~~
b181d57f 3088
a6e5ef7d 3089If you receive the SHA-1 name of a blob from one source, and its contents
1bbf1c79 3090from another (possibly untrusted) source, you can still trust that those
a6e5ef7d
FC
3091contents are correct as long as the SHA-1 name agrees. This is because
3092the SHA-1 is designed so that it is infeasible to find different contents
1bbf1c79 3093that produce the same hash.
b181d57f 3094
a6e5ef7d 3095Similarly, you need only trust the SHA-1 name of a top-level tree object
1bbf1c79 3096to trust the contents of the entire directory that it refers to, and if
a6e5ef7d 3097you receive the SHA-1 name of a commit from a trusted source, then you
1bbf1c79
BF
3098can easily verify the entire history of commits reachable through
3099parents of that commit, and all of those contents of the trees referred
3100to by those commits.
b181d57f
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3101
3102So to introduce some real trust in the system, the only thing you need
3103to do is to digitally sign just 'one' special note, which includes the
3104name of a top-level commit. Your digital signature shows others
3105that you trust that commit, and the immutability of the history of
3106commits tells others that they can trust the whole history.
3107
3108In other words, you can easily validate a whole archive by just
a6e5ef7d 3109sending out a single email that tells the people the name (SHA-1 hash)
b181d57f
BF
3110of the top commit, and digitally sign that email using something
3111like GPG/PGP.
3112
3113To assist in this, git also provides the tag object...
3114
e34caace 3115[[tag-object]]
b181d57f 3116Tag Object
971aa71f 3117~~~~~~~~~~
b181d57f 3118
1bbf1c79
BF
3119A tag object contains an object, object type, tag name, the name of the
3120person ("tagger") who created the tag, and a message, which may contain
843c81dc 3121a signature, as can be seen using linkgit:git-cat-file[1]:
b181d57f 3122
1bbf1c79
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3123------------------------------------------------
3124$ git cat-file tag v1.5.0
3125object 437b1b20df4b356c9342dac8d38849f24ef44f27
3126type commit
3127tag v1.5.0
3128tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000
3129
3130GIT 1.5.0
3131-----BEGIN PGP SIGNATURE-----
3132Version: GnuPG v1.4.6 (GNU/Linux)
3133
3134iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui
3135nLE/L9aUXdWeTFPron96DLA=
3136=2E+0
3137-----END PGP SIGNATURE-----
3138------------------------------------------------
b181d57f 3139
5162e697
DM
3140See the linkgit:git-tag[1] command to learn how to create and verify tag
3141objects. (Note that linkgit:git-tag[1] can also be used to create
1bbf1c79 3142"lightweight tags", which are not tag objects at all, but just simple
fc74ecc1 3143references whose names begin with "refs/tags/").
b181d57f 3144
09eff7b0
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3145[[pack-files]]
3146How git stores objects efficiently: pack files
3147~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3148
9644ffdd 3149Newly created objects are initially created in a file named after the
a6e5ef7d 3150object's SHA-1 hash (stored in .git/objects).
09eff7b0
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3151
3152Unfortunately this system becomes inefficient once a project has a
3153lot of objects. Try this on an old project:
3154
3155------------------------------------------------
3156$ git count-objects
31576930 objects, 47620 kilobytes
3158------------------------------------------------
3159
3160The first number is the number of objects which are kept in
3161individual files. The second is the amount of space taken up by
3162those "loose" objects.
3163
3164You can save space and make git faster by moving these loose objects in
3165to a "pack file", which stores a group of objects in an efficient
3166compressed format; the details of how pack files are formatted can be
3167found in link:technical/pack-format.txt[technical/pack-format.txt].
3168
3169To put the loose objects into a pack, just run git repack:
3170
3171------------------------------------------------
3172$ git repack
3173Generating pack...
3174Done counting 6020 objects.
3175Deltifying 6020 objects.
3176 100% (6020/6020) done
3177Writing 6020 objects.
3178 100% (6020/6020) done
3179Total 6020, written 6020 (delta 4070), reused 0 (delta 0)
3180Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.
3181------------------------------------------------
3182
3183You can then run
3184
3185------------------------------------------------
3186$ git prune
3187------------------------------------------------
3188
3189to remove any of the "loose" objects that are now contained in the
3190pack. This will also remove any unreferenced objects (which may be
6127c086 3191created when, for example, you use "git reset" to remove a commit).
09eff7b0
BF
3192You can verify that the loose objects are gone by looking at the
3193.git/objects directory or by running
3194
3195------------------------------------------------
3196$ git count-objects
31970 objects, 0 kilobytes
3198------------------------------------------------
3199
3200Although the object files are gone, any commands that refer to those
3201objects will work exactly as they did before.
3202
5162e697 3203The linkgit:git-gc[1] command performs packing, pruning, and more for
09eff7b0
BF
3204you, so is normally the only high-level command you need.
3205
3206[[dangling-objects]]
3207Dangling objects
3208~~~~~~~~~~~~~~~~
3209
5162e697 3210The linkgit:git-fsck[1] command will sometimes complain about dangling
09eff7b0
BF
3211objects. They are not a problem.
3212
3213The most common cause of dangling objects is that you've rebased a
3214branch, or you have pulled from somebody else who rebased a branch--see
3215<<cleaning-up-history>>. In that case, the old head of the original
3216branch still exists, as does everything it pointed to. The branch
3217pointer itself just doesn't, since you replaced it with another one.
3218
3219There are also other situations that cause dangling objects. For
6127c086 3220example, a "dangling blob" may arise because you did a "git add" of a
09eff7b0
BF
3221file, but then, before you actually committed it and made it part of the
3222bigger picture, you changed something else in that file and committed
2ef8ac1b 3223that *updated* thing--the old state that you added originally ends up
09eff7b0
BF
3224not being pointed to by any commit or tree, so it's now a dangling blob
3225object.
3226
3227Similarly, when the "recursive" merge strategy runs, and finds that
3228there are criss-cross merges and thus more than one merge base (which is
3229fairly unusual, but it does happen), it will generate one temporary
3230midway tree (or possibly even more, if you had lots of criss-crossing
3231merges and more than two merge bases) as a temporary internal merge
3232base, and again, those are real objects, but the end result will not end
3233up pointing to them, so they end up "dangling" in your repository.
3234
3235Generally, dangling objects aren't anything to worry about. They can
3236even be very useful: if you screw something up, the dangling objects can
3237be how you recover your old tree (say, you did a rebase, and realized
2ef8ac1b 3238that you really didn't want to--you can look at what dangling objects
09eff7b0
BF
3239you have, and decide to reset your head to some old dangling state).
3240
3241For commits, you can just use:
3242
3243------------------------------------------------
3244$ gitk <dangling-commit-sha-goes-here> --not --all
3245------------------------------------------------
3246
3247This asks for all the history reachable from the given commit but not
3248from any branch, tag, or other reference. If you decide it's something
3249you want, you can always create a new reference to it, e.g.,
3250
3251------------------------------------------------
3252$ git branch recovered-branch <dangling-commit-sha-goes-here>
3253------------------------------------------------
3254
3255For blobs and trees, you can't do the same, but you can still examine
3256them. You can just do
3257
3258------------------------------------------------
3259$ git show <dangling-blob/tree-sha-goes-here>
3260------------------------------------------------
3261
3262to show what the contents of the blob were (or, for a tree, basically
3263what the "ls" for that directory was), and that may give you some idea
3264of what the operation was that left that dangling object.
3265
3266Usually, dangling blobs and trees aren't very interesting. They're
3267almost always the result of either being a half-way mergebase (the blob
3268will often even have the conflict markers from a merge in it, if you
3269have had conflicting merges that you fixed up by hand), or simply
6127c086 3270because you interrupted a "git fetch" with ^C or something like that,
09eff7b0
BF
3271leaving _some_ of the new objects in the object database, but just
3272dangling and useless.
3273
3274Anyway, once you are sure that you're not interested in any dangling
3275state, you can just prune all unreachable objects:
3276
3277------------------------------------------------
3278$ git prune
3279------------------------------------------------
3280
3281and they'll be gone. But you should only run "git prune" on a quiescent
2ef8ac1b 3282repository--it's kind of like doing a filesystem fsck recovery: you
09eff7b0
BF
3283don't want to do that while the filesystem is mounted.
3284
6127c086
FC
3285(The same is true of "git fsck" itself, btw, but since
3286`git fsck` never actually *changes* the repository, it just reports
3287on what it found, `git fsck` itself is never