Merge branch 'pw/rerere-autoupdate'
[git/git.git] / Documentation / git-merge.txt
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1git-merge(1)
2============
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3
4NAME
5----
c3f0baac 6git-merge - Join two or more development histories together
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7
8
9SYNOPSIS
10--------
17bcdad3 11[verse]
f8246281 12'git merge' [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
340f2c5e 13 [-s <strategy>] [-X <strategy-option>] [-S[<keyid>]]
09c2cb87 14 [--[no-]allow-unrelated-histories]
920f22e6 15 [--[no-]rerere-autoupdate] [-m <msg>] [-F <file>] [<commit>...]
35d2fffd 16'git merge' --abort
367ff694 17'git merge' --continue
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18
19DESCRIPTION
20-----------
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21Incorporates changes from the named commits (since the time their
22histories diverged from the current branch) into the current
23branch. This command is used by 'git pull' to incorporate changes
24from another repository and can be used by hand to merge changes
25from one branch into another.
26
27Assume the following history exists and the current branch is
28"`master`":
29
30------------
31 A---B---C topic
32 /
33 D---E---F---G master
34------------
35
36Then "`git merge topic`" will replay the changes made on the
37`topic` branch since it diverged from `master` (i.e., `E`) until
38its current commit (`C`) on top of `master`, and record the result
39in a new commit along with the names of the two parent commits and
40a log message from the user describing the changes.
41
42------------
43 A---B---C topic
44 / \
45 D---E---F---G---H master
46------------
0f69be53 47
b4391657 48The second syntax ("`git merge --abort`") can only be run after the
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49merge has resulted in conflicts. 'git merge --abort' will abort the
50merge process and try to reconstruct the pre-merge state. However,
51if there were uncommitted changes when the merge started (and
52especially if those changes were further modified after the merge
53was started), 'git merge --abort' will in some cases be unable to
54reconstruct the original (pre-merge) changes. Therefore:
55
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56*Warning*: Running 'git merge' with non-trivial uncommitted changes is
57discouraged: while possible, it may leave you in a state that is hard to
e330d8ca 58back out of in the case of a conflict.
dee48c3c 59
28cb0602 60The third syntax ("`git merge --continue`") can only be run after the
367ff694 61merge has resulted in conflicts.
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62
63OPTIONS
64-------
93d69d86 65include::merge-options.txt[]
0f69be53 66
dee48c3c 67-m <msg>::
0f8a02c6 68 Set the commit message to be used for the merge commit (in
f0ecac2b 69 case one is created).
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70+
71If `--log` is specified, a shortlog of the commits being merged
72will be appended to the specified message.
73+
74The 'git fmt-merge-msg' command can be
75used to give a good default for automated 'git merge'
561d2b79 76invocations. The automated message can include the branch description.
3c64314c 77
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78-F <file>::
79--file=<file>::
80 Read the commit message to be used for the merge commit (in
81 case one is created).
82+
83If `--log` is specified, a shortlog of the commits being merged
84will be appended to the specified message.
85
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86--rerere-autoupdate::
87--no-rerere-autoupdate::
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88 Allow the rerere mechanism to update the index with the
89 result of auto-conflict resolution if possible.
90
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91--abort::
92 Abort the current conflict resolution process, and
93 try to reconstruct the pre-merge state.
94+
95If there were uncommitted worktree changes present when the merge
96started, 'git merge --abort' will in some cases be unable to
97reconstruct these changes. It is therefore recommended to always
98commit or stash your changes before running 'git merge'.
99+
100'git merge --abort' is equivalent to 'git reset --merge' when
101`MERGE_HEAD` is present.
102
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103--continue::
104 After a 'git merge' stops due to conflicts you can conclude the
105 merge by running 'git merge --continue' (see "HOW TO RESOLVE
106 CONFLICTS" section below).
107
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108<commit>...::
109 Commits, usually other branch heads, to merge into our branch.
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110 Specifying more than one commit will create a merge with
111 more than two parents (affectionately called an Octopus merge).
112+
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113If no commit is given from the command line, merge the remote-tracking
114branches that the current branch is configured to use as its upstream.
93e535a5 115See also the configuration section of this manual page.
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117When `FETCH_HEAD` (and no other commit) is specified, the branches
118recorded in the `.git/FETCH_HEAD` file by the previous invocation
119of `git fetch` for merging are merged to the current branch.
0f69be53 120
bb73d73c 121
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122PRE-MERGE CHECKS
123----------------
0f69be53 124
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125Before applying outside changes, you should get your own work in
126good shape and committed locally, so it will not be clobbered if
127there are conflicts. See also linkgit:git-stash[1].
128'git pull' and 'git merge' will stop without doing anything when
129local uncommitted changes overlap with files that 'git pull'/'git
130merge' may need to update.
3ae854c3 131
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132To avoid recording unrelated changes in the merge commit,
133'git pull' and 'git merge' will also abort if there are any changes
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134registered in the index relative to the `HEAD` commit. (Special
135narrow exceptions to this rule may exist depending on which merge
136strategy is in use, but generally, the index must match HEAD.)
dbddb714 137
30f2bade 138If all named commits are already ancestors of `HEAD`, 'git merge'
7560f547 139will exit early with the message "Already up to date."
3ae854c3 140
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141FAST-FORWARD MERGE
142------------------
143
144Often the current branch head is an ancestor of the named commit.
145This is the most common case especially when invoked from 'git
146pull': you are tracking an upstream repository, you have committed
147no local changes, and now you want to update to a newer upstream
148revision. In this case, a new commit is not needed to store the
149combined history; instead, the `HEAD` (along with the index) is
150updated to point at the named commit, without creating an extra
151merge commit.
152
153This behavior can be suppressed with the `--no-ff` option.
ffb1a4be 154
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155TRUE MERGE
156----------
c0be8aa0 157
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158Except in a fast-forward merge (see above), the branches to be
159merged must be tied together by a merge commit that has both of them
160as its parents.
ffb1a4be 161
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162A merged version reconciling the changes from all branches to be
163merged is committed, and your `HEAD`, index, and working tree are
164updated to it. It is possible to have modifications in the working
165tree as long as they do not overlap; the update will preserve them.
ffb1a4be 166
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167When it is not obvious how to reconcile the changes, the following
168happens:
ffb1a4be 169
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1701. The `HEAD` pointer stays the same.
1712. The `MERGE_HEAD` ref is set to point to the other branch head.
1723. Paths that merged cleanly are updated both in the index file and
ffb1a4be 173 in your working tree.
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1744. For conflicting paths, the index file records up to three
175 versions: stage 1 stores the version from the common ancestor,
176 stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
b1889c36 177 can inspect the stages with `git ls-files -u`). The working
29b802aa 178 tree files contain the result of the "merge" program; i.e. 3-way
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179 merge results with familiar conflict markers `<<<` `===` `>>>`.
1805. No other changes are made. In particular, the local
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181 modifications you had before you started merge will stay the
182 same and the index entries for them stay as they were,
183 i.e. matching `HEAD`.
184
ed4a6baa 185If you tried a merge which resulted in complex conflicts and
35d2fffd 186want to start over, you can recover with `git merge --abort`.
ed4a6baa 187
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188MERGING TAG
189-----------
190
191When merging an annotated (and possibly signed) tag, Git always
192creates a merge commit even if a fast-forward merge is possible, and
193the commit message template is prepared with the tag message.
194Additionally, if the tag is signed, the signature check is reported
195as a comment in the message template. See also linkgit:git-tag[1].
196
197When you want to just integrate with the work leading to the commit
198that happens to be tagged, e.g. synchronizing with an upstream
199release point, you may not want to make an unnecessary merge commit.
200
201In such a case, you can "unwrap" the tag yourself before feeding it
202to `git merge`, or pass `--ff-only` when you do not have any work on
203your own. e.g.
204
e45bda87 205----
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206git fetch origin
207git merge v1.2.3^0
208git merge --ff-only v1.2.3
e45bda87 209----
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210
211
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212HOW CONFLICTS ARE PRESENTED
213---------------------------
214
215During a merge, the working tree files are updated to reflect the result
216of the merge. Among the changes made to the common ancestor's version,
217non-overlapping ones (that is, you changed an area of the file while the
218other side left that area intact, or vice versa) are incorporated in the
219final result verbatim. When both sides made changes to the same area,
2de9b711 220however, Git cannot randomly pick one side over the other, and asks you to
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221resolve it by leaving what both sides did to that area.
222
2de9b711 223By default, Git uses the same style as the one used by the "merge" program
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224from the RCS suite to present such a conflicted hunk, like this:
225
226------------
227Here are lines that are either unchanged from the common
228ancestor, or cleanly resolved because only one side changed.
229<<<<<<< yours:sample.txt
230Conflict resolution is hard;
231let's go shopping.
232=======
233Git makes conflict resolution easy.
234>>>>>>> theirs:sample.txt
235And here is another line that is cleanly resolved or unmodified.
236------------
237
29b802aa 238The area where a pair of conflicting changes happened is marked with markers
dcb11263 239`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
29b802aa 240is typically your side, and the part afterwards is typically their side.
70a3f897 241
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242The default format does not show what the original said in the conflicting
243area. You cannot tell how many lines are deleted and replaced with
244Barbie's remark on your side. The only thing you can tell is that your
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245side wants to say it is hard and you'd prefer to go shopping, while the
246other side wants to claim it is easy.
247
da0005b8 248An alternative style can be used by setting the "merge.conflictStyle"
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249configuration variable to "diff3". In "diff3" style, the above conflict
250may look like this:
251
252------------
253Here are lines that are either unchanged from the common
254ancestor, or cleanly resolved because only one side changed.
255<<<<<<< yours:sample.txt
256Conflict resolution is hard;
257let's go shopping.
258|||||||
259Conflict resolution is hard.
260=======
261Git makes conflict resolution easy.
262>>>>>>> theirs:sample.txt
263And here is another line that is cleanly resolved or unmodified.
264------------
265
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266In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
267another `|||||||` marker that is followed by the original text. You can
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268tell that the original just stated a fact, and your side simply gave in to
269that statement and gave up, while the other side tried to have a more
270positive attitude. You can sometimes come up with a better resolution by
271viewing the original.
272
273
274HOW TO RESOLVE CONFLICTS
275------------------------
276
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277After seeing a conflict, you can do two things:
278
29b802aa 279 * Decide not to merge. The only clean-ups you need are to reset
ffb1a4be 280 the index file to the `HEAD` commit to reverse 2. and to clean
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281 up working tree changes made by 2. and 3.; `git merge --abort`
282 can be used for this.
ffb1a4be 283
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284 * Resolve the conflicts. Git will mark the conflicts in
285 the working tree. Edit the files into shape and
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286 'git add' them to the index. Use 'git commit' or
287 'git merge --continue' to seal the deal. The latter command
288 checks whether there is a (interrupted) merge in progress
289 before calling 'git commit'.
ffb1a4be 290
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291You can work through the conflict with a number of tools:
292
ca768288 293 * Use a mergetool. `git mergetool` to launch a graphical
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294 mergetool which will work you through the merge.
295
ca768288 296 * Look at the diffs. `git diff` will show a three-way diff,
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297 highlighting changes from both the `HEAD` and `MERGE_HEAD`
298 versions.
34ad1afa 299
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300 * Look at the diffs from each branch. `git log --merge -p <path>`
301 will show diffs first for the `HEAD` version and then the
302 `MERGE_HEAD` version.
34ad1afa 303
ca768288 304 * Look at the originals. `git show :1:filename` shows the
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305 common ancestor, `git show :2:filename` shows the `HEAD`
306 version, and `git show :3:filename` shows the `MERGE_HEAD`
307 version.
ffb1a4be 308
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309
310EXAMPLES
311--------
312
313* Merge branches `fixes` and `enhancements` on top of
314 the current branch, making an octopus merge:
315+
316------------------------------------------------
317$ git merge fixes enhancements
318------------------------------------------------
319
320* Merge branch `obsolete` into the current branch, using `ours`
321 merge strategy:
322+
323------------------------------------------------
324$ git merge -s ours obsolete
325------------------------------------------------
326
327* Merge branch `maint` into the current branch, but do not make
328 a new commit automatically:
329+
330------------------------------------------------
331$ git merge --no-commit maint
332------------------------------------------------
333+
334This can be used when you want to include further changes to the
335merge, or want to write your own merge commit message.
336+
337You should refrain from abusing this option to sneak substantial
338changes into a merge commit. Small fixups like bumping
339release/version name would be acceptable.
340
341
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342include::merge-strategies.txt[]
343
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344CONFIGURATION
345-------------
7fb5ab4a 346include::config/merge.txt[]
35e9d630 347
da0005b8 348branch.<name>.mergeOptions::
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349 Sets default options for merging into branch <name>. The syntax and
350 supported options are the same as those of 'git merge', but option
351 values containing whitespace characters are currently not supported.
352
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353SEE ALSO
354--------
5162e697 355linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
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356linkgit:gitattributes[5],
357linkgit:git-reset[1],
358linkgit:git-diff[1], linkgit:git-ls-files[1],
359linkgit:git-add[1], linkgit:git-rm[1],
360linkgit:git-mergetool[1]
3c64314c 361
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362GIT
363---
9e1f0a85 364Part of the linkgit:git[1] suite