Merge branch 'maint-1.7.4' into maint-1.7.5
[git/git.git] / Documentation / git-checkout.txt
1 git-checkout(1)
2 ===============
3
4 NAME
5 ----
6 git-checkout - Checkout a branch or paths to the working tree
7
8 SYNOPSIS
9 --------
10 [verse]
11 'git checkout' [-q] [-f] [-m] [<branch>]
12 'git checkout' [-q] [-f] [-m] [--detach] [<commit>]
13 'git checkout' [-q] [-f] [-m] [[-b|-B|--orphan] <new_branch>] [<start_point>]
14 'git checkout' [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <paths>...
15 'git checkout' [-p|--patch] [<tree-ish>] [--] [<paths>...]
16
17 DESCRIPTION
18 -----------
19 Updates files in the working tree to match the version in the index
20 or the specified tree. If no paths are given, 'git checkout' will
21 also update `HEAD` to set the specified branch as the current
22 branch.
23
24 'git checkout' [<branch>]::
25 'git checkout' -b|-B <new_branch> [<start point>]::
26 'git checkout' [--detach] [<commit>]::
27
28 This form switches branches by updating the index, working
29 tree, and HEAD to reflect the specified branch or commit.
30 +
31 If `-b` is given, a new branch is created as if linkgit:git-branch[1]
32 were called and then checked out; in this case you can
33 use the `--track` or `--no-track` options, which will be passed to
34 'git branch'. As a convenience, `--track` without `-b` implies branch
35 creation; see the description of `--track` below.
36 +
37 If `-B` is given, <new_branch> is created if it doesn't exist; otherwise, it
38 is reset. This is the transactional equivalent of
39 +
40 ------------
41 $ git branch -f <branch> [<start point>]
42 $ git checkout <branch>
43 ------------
44 +
45 that is to say, the branch is not reset/created unless "git checkout" is
46 successful.
47
48 'git checkout' [-p|--patch] [<tree-ish>] [--] <pathspec>...::
49
50 When <paths> or `--patch` are given, 'git checkout' does *not*
51 switch branches. It updates the named paths in the working tree
52 from the index file or from a named <tree-ish> (most often a
53 commit). In this case, the `-b` and `--track` options are
54 meaningless and giving either of them results in an error. The
55 <tree-ish> argument can be used to specify a specific tree-ish
56 (i.e. commit, tag or tree) to update the index for the given
57 paths before updating the working tree.
58 +
59 The index may contain unmerged entries because of a previous failed merge.
60 By default, if you try to check out such an entry from the index, the
61 checkout operation will fail and nothing will be checked out.
62 Using `-f` will ignore these unmerged entries. The contents from a
63 specific side of the merge can be checked out of the index by
64 using `--ours` or `--theirs`. With `-m`, changes made to the working tree
65 file can be discarded to re-create the original conflicted merge result.
66
67 OPTIONS
68 -------
69 -q::
70 --quiet::
71 Quiet, suppress feedback messages.
72
73 -f::
74 --force::
75 When switching branches, proceed even if the index or the
76 working tree differs from HEAD. This is used to throw away
77 local changes.
78 +
79 When checking out paths from the index, do not fail upon unmerged
80 entries; instead, unmerged entries are ignored.
81
82 --ours::
83 --theirs::
84 When checking out paths from the index, check out stage #2
85 ('ours') or #3 ('theirs') for unmerged paths.
86
87 -b::
88 Create a new branch named <new_branch> and start it at
89 <start_point>; see linkgit:git-branch[1] for details.
90
91 -B::
92 Creates the branch <new_branch> and start it at <start_point>;
93 if it already exists, then reset it to <start_point>. This is
94 equivalent to running "git branch" with "-f"; see
95 linkgit:git-branch[1] for details.
96
97 -t::
98 --track::
99 When creating a new branch, set up "upstream" configuration. See
100 "--track" in linkgit:git-branch[1] for details.
101 +
102 If no '-b' option is given, the name of the new branch will be
103 derived from the remote-tracking branch. If "remotes/" or "refs/remotes/"
104 is prefixed it is stripped away, and then the part up to the
105 next slash (which would be the nickname of the remote) is removed.
106 This would tell us to use "hack" as the local branch when branching
107 off of "origin/hack" (or "remotes/origin/hack", or even
108 "refs/remotes/origin/hack"). If the given name has no slash, or the above
109 guessing results in an empty name, the guessing is aborted. You can
110 explicitly give a name with '-b' in such a case.
111
112 --no-track::
113 Do not set up "upstream" configuration, even if the
114 branch.autosetupmerge configuration variable is true.
115
116 -l::
117 Create the new branch's reflog; see linkgit:git-branch[1] for
118 details.
119
120 --detach::
121 Rather than checking out a branch to work on it, check out a
122 commit for inspection and discardable experiments.
123 This is the default behavior of "git checkout <commit>" when
124 <commit> is not a branch name. See the "DETACHED HEAD" section
125 below for details.
126
127 --orphan::
128 Create a new 'orphan' branch, named <new_branch>, started from
129 <start_point> and switch to it. The first commit made on this
130 new branch will have no parents and it will be the root of a new
131 history totally disconnected from all the other branches and
132 commits.
133 +
134 The index and the working tree are adjusted as if you had previously run
135 "git checkout <start_point>". This allows you to start a new history
136 that records a set of paths similar to <start_point> by easily running
137 "git commit -a" to make the root commit.
138 +
139 This can be useful when you want to publish the tree from a commit
140 without exposing its full history. You might want to do this to publish
141 an open source branch of a project whose current tree is "clean", but
142 whose full history contains proprietary or otherwise encumbered bits of
143 code.
144 +
145 If you want to start a disconnected history that records a set of paths
146 that is totally different from the one of <start_point>, then you should
147 clear the index and the working tree right after creating the orphan
148 branch by running "git rm -rf ." from the top level of the working tree.
149 Afterwards you will be ready to prepare your new files, repopulating the
150 working tree, by copying them from elsewhere, extracting a tarball, etc.
151
152 -m::
153 --merge::
154 When switching branches,
155 if you have local modifications to one or more files that
156 are different between the current branch and the branch to
157 which you are switching, the command refuses to switch
158 branches in order to preserve your modifications in context.
159 However, with this option, a three-way merge between the current
160 branch, your working tree contents, and the new branch
161 is done, and you will be on the new branch.
162 +
163 When a merge conflict happens, the index entries for conflicting
164 paths are left unmerged, and you need to resolve the conflicts
165 and mark the resolved paths with `git add` (or `git rm` if the merge
166 should result in deletion of the path).
167 +
168 When checking out paths from the index, this option lets you recreate
169 the conflicted merge in the specified paths.
170
171 --conflict=<style>::
172 The same as --merge option above, but changes the way the
173 conflicting hunks are presented, overriding the
174 merge.conflictstyle configuration variable. Possible values are
175 "merge" (default) and "diff3" (in addition to what is shown by
176 "merge" style, shows the original contents).
177
178 -p::
179 --patch::
180 Interactively select hunks in the difference between the
181 <tree-ish> (or the index, if unspecified) and the working
182 tree. The chosen hunks are then applied in reverse to the
183 working tree (and if a <tree-ish> was specified, the index).
184 +
185 This means that you can use `git checkout -p` to selectively discard
186 edits from your current working tree. See the ``Interactive Mode''
187 section of linkgit:git-add[1] to learn how to operate the `\--patch` mode.
188
189 <branch>::
190 Branch to checkout; if it refers to a branch (i.e., a name that,
191 when prepended with "refs/heads/", is a valid ref), then that
192 branch is checked out. Otherwise, if it refers to a valid
193 commit, your HEAD becomes "detached" and you are no longer on
194 any branch (see below for details).
195 +
196 As a special case, the `"@\{-N\}"` syntax for the N-th last branch
197 checks out the branch (instead of detaching). You may also specify
198 `-` which is synonymous with `"@\{-1\}"`.
199 +
200 As a further special case, you may use `"A\...B"` as a shortcut for the
201 merge base of `A` and `B` if there is exactly one merge base. You can
202 leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
203
204 <new_branch>::
205 Name for the new branch.
206
207 <start_point>::
208 The name of a commit at which to start the new branch; see
209 linkgit:git-branch[1] for details. Defaults to HEAD.
210
211 <tree-ish>::
212 Tree to checkout from (when paths are given). If not specified,
213 the index will be used.
214
215
216
217 DETACHED HEAD
218 -------------
219 HEAD normally refers to a named branch (e.g. 'master'). Meanwhile, each
220 branch refers to a specific commit. Let's look at a repo with three
221 commits, one of them tagged, and with branch 'master' checked out:
222
223 ------------
224 HEAD (refers to branch 'master')
225 |
226 v
227 a---b---c branch 'master' (refers to commit 'c')
228 ^
229 |
230 tag 'v2.0' (refers to commit 'b')
231 ------------
232
233 When a commit is created in this state, the branch is updated to refer to
234 the new commit. Specifically, 'git commit' creates a new commit 'd', whose
235 parent is commit 'c', and then updates branch 'master' to refer to new
236 commit 'd'. HEAD still refers to branch 'master' and so indirectly now refers
237 to commit 'd':
238
239 ------------
240 $ edit; git add; git commit
241
242 HEAD (refers to branch 'master')
243 |
244 v
245 a---b---c---d branch 'master' (refers to commit 'd')
246 ^
247 |
248 tag 'v2.0' (refers to commit 'b')
249 ------------
250
251 It is sometimes useful to be able to checkout a commit that is not at
252 the tip of any named branch, or even to create a new commit that is not
253 referenced by a named branch. Let's look at what happens when we
254 checkout commit 'b' (here we show two ways this may be done):
255
256 ------------
257 $ git checkout v2.0 # or
258 $ git checkout master^^
259
260 HEAD (refers to commit 'b')
261 |
262 v
263 a---b---c---d branch 'master' (refers to commit 'd')
264 ^
265 |
266 tag 'v2.0' (refers to commit 'b')
267 ------------
268
269 Notice that regardless of which checkout command we use, HEAD now refers
270 directly to commit 'b'. This is known as being in detached HEAD state.
271 It means simply that HEAD refers to a specific commit, as opposed to
272 referring to a named branch. Let's see what happens when we create a commit:
273
274 ------------
275 $ edit; git add; git commit
276
277 HEAD (refers to commit 'e')
278 |
279 v
280 e
281 /
282 a---b---c---d branch 'master' (refers to commit 'd')
283 ^
284 |
285 tag 'v2.0' (refers to commit 'b')
286 ------------
287
288 There is now a new commit 'e', but it is referenced only by HEAD. We can
289 of course add yet another commit in this state:
290
291 ------------
292 $ edit; git add; git commit
293
294 HEAD (refers to commit 'f')
295 |
296 v
297 e---f
298 /
299 a---b---c---d branch 'master' (refers to commit 'd')
300 ^
301 |
302 tag 'v2.0' (refers to commit 'b')
303 ------------
304
305 In fact, we can perform all the normal git operations. But, let's look
306 at what happens when we then checkout master:
307
308 ------------
309 $ git checkout master
310
311 HEAD (refers to branch 'master')
312 e---f |
313 / v
314 a---b---c---d branch 'master' (refers to commit 'd')
315 ^
316 |
317 tag 'v2.0' (refers to commit 'b')
318 ------------
319
320 It is important to realize that at this point nothing refers to commit
321 'f'. Eventually commit 'f' (and by extension commit 'e') will be deleted
322 by the routine git garbage collection process, unless we create a reference
323 before that happens. If we have not yet moved away from commit 'f',
324 any of these will create a reference to it:
325
326 ------------
327 $ git checkout -b foo <1>
328 $ git branch foo <2>
329 $ git tag foo <3>
330 ------------
331
332 <1> creates a new branch 'foo', which refers to commit 'f', and then
333 updates HEAD to refer to branch 'foo'. In other words, we'll no longer
334 be in detached HEAD state after this command.
335
336 <2> similarly creates a new branch 'foo', which refers to commit 'f',
337 but leaves HEAD detached.
338
339 <3> creates a new tag 'foo', which refers to commit 'f',
340 leaving HEAD detached.
341
342 If we have moved away from commit 'f', then we must first recover its object
343 name (typically by using git reflog), and then we can create a reference to
344 it. For example, to see the last two commits to which HEAD referred, we
345 can use either of these commands:
346
347 ------------
348 $ git reflog -2 HEAD # or
349 $ git log -g -2 HEAD
350 ------------
351
352 EXAMPLES
353 --------
354
355 . The following sequence checks out the `master` branch, reverts
356 the `Makefile` to two revisions back, deletes hello.c by
357 mistake, and gets it back from the index.
358 +
359 ------------
360 $ git checkout master <1>
361 $ git checkout master~2 Makefile <2>
362 $ rm -f hello.c
363 $ git checkout hello.c <3>
364 ------------
365 +
366 <1> switch branch
367 <2> take a file out of another commit
368 <3> restore hello.c from the index
369 +
370 If you have an unfortunate branch that is named `hello.c`, this
371 step would be confused as an instruction to switch to that branch.
372 You should instead write:
373 +
374 ------------
375 $ git checkout -- hello.c
376 ------------
377
378 . After working in the wrong branch, switching to the correct
379 branch would be done using:
380 +
381 ------------
382 $ git checkout mytopic
383 ------------
384 +
385 However, your "wrong" branch and correct "mytopic" branch may
386 differ in files that you have modified locally, in which case
387 the above checkout would fail like this:
388 +
389 ------------
390 $ git checkout mytopic
391 error: You have local changes to 'frotz'; not switching branches.
392 ------------
393 +
394 You can give the `-m` flag to the command, which would try a
395 three-way merge:
396 +
397 ------------
398 $ git checkout -m mytopic
399 Auto-merging frotz
400 ------------
401 +
402 After this three-way merge, the local modifications are _not_
403 registered in your index file, so `git diff` would show you what
404 changes you made since the tip of the new branch.
405
406 . When a merge conflict happens during switching branches with
407 the `-m` option, you would see something like this:
408 +
409 ------------
410 $ git checkout -m mytopic
411 Auto-merging frotz
412 ERROR: Merge conflict in frotz
413 fatal: merge program failed
414 ------------
415 +
416 At this point, `git diff` shows the changes cleanly merged as in
417 the previous example, as well as the changes in the conflicted
418 files. Edit and resolve the conflict and mark it resolved with
419 `git add` as usual:
420 +
421 ------------
422 $ edit frotz
423 $ git add frotz
424 ------------
425
426 GIT
427 ---
428 Part of the linkgit:git[1] suite