Git 2.14.1
[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]
93e535a5 15 [--[no-]rerere-autoupdate] [-m <msg>] [<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
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60The fourth syntax ("`git merge --continue`") can only be run after the
61merge has resulted in conflicts.
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62
63OPTIONS
64-------
93d69d86 65include::merge-options.txt[]
0f69be53 66
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67-S[<keyid>]::
68--gpg-sign[=<keyid>]::
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69 GPG-sign the resulting merge commit. The `keyid` argument is
70 optional and defaults to the committer identity; if specified,
71 it must be stuck to the option without a space.
5f737ac9 72
dee48c3c 73-m <msg>::
0f8a02c6 74 Set the commit message to be used for the merge commit (in
f0ecac2b 75 case one is created).
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76+
77If `--log` is specified, a shortlog of the commits being merged
78will be appended to the specified message.
79+
80The 'git fmt-merge-msg' command can be
81used to give a good default for automated 'git merge'
561d2b79 82invocations. The automated message can include the branch description.
3c64314c 83
0460ed2c 84--[no-]rerere-autoupdate::
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85 Allow the rerere mechanism to update the index with the
86 result of auto-conflict resolution if possible.
87
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88--abort::
89 Abort the current conflict resolution process, and
90 try to reconstruct the pre-merge state.
91+
92If there were uncommitted worktree changes present when the merge
93started, 'git merge --abort' will in some cases be unable to
94reconstruct these changes. It is therefore recommended to always
95commit or stash your changes before running 'git merge'.
96+
97'git merge --abort' is equivalent to 'git reset --merge' when
98`MERGE_HEAD` is present.
99
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100--continue::
101 After a 'git merge' stops due to conflicts you can conclude the
102 merge by running 'git merge --continue' (see "HOW TO RESOLVE
103 CONFLICTS" section below).
104
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105<commit>...::
106 Commits, usually other branch heads, to merge into our branch.
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107 Specifying more than one commit will create a merge with
108 more than two parents (affectionately called an Octopus merge).
109+
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110If no commit is given from the command line, merge the remote-tracking
111branches that the current branch is configured to use as its upstream.
93e535a5 112See also the configuration section of this manual page.
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113+
114When `FETCH_HEAD` (and no other commit) is specified, the branches
115recorded in the `.git/FETCH_HEAD` file by the previous invocation
116of `git fetch` for merging are merged to the current branch.
0f69be53 117
bb73d73c 118
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119PRE-MERGE CHECKS
120----------------
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122Before applying outside changes, you should get your own work in
123good shape and committed locally, so it will not be clobbered if
124there are conflicts. See also linkgit:git-stash[1].
125'git pull' and 'git merge' will stop without doing anything when
126local uncommitted changes overlap with files that 'git pull'/'git
127merge' may need to update.
3ae854c3 128
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129To avoid recording unrelated changes in the merge commit,
130'git pull' and 'git merge' will also abort if there are any changes
131registered in the index relative to the `HEAD` commit. (One
132exception is when the changed index entries are in the state that
133would result from the merge already.)
dbddb714 134
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135If all named commits are already ancestors of `HEAD`, 'git merge'
136will exit early with the message "Already up-to-date."
3ae854c3 137
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138FAST-FORWARD MERGE
139------------------
140
141Often the current branch head is an ancestor of the named commit.
142This is the most common case especially when invoked from 'git
143pull': you are tracking an upstream repository, you have committed
144no local changes, and now you want to update to a newer upstream
145revision. In this case, a new commit is not needed to store the
146combined history; instead, the `HEAD` (along with the index) is
147updated to point at the named commit, without creating an extra
148merge commit.
149
150This behavior can be suppressed with the `--no-ff` option.
ffb1a4be 151
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152TRUE MERGE
153----------
c0be8aa0 154
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155Except in a fast-forward merge (see above), the branches to be
156merged must be tied together by a merge commit that has both of them
157as its parents.
ffb1a4be 158
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159A merged version reconciling the changes from all branches to be
160merged is committed, and your `HEAD`, index, and working tree are
161updated to it. It is possible to have modifications in the working
162tree as long as they do not overlap; the update will preserve them.
ffb1a4be 163
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164When it is not obvious how to reconcile the changes, the following
165happens:
ffb1a4be 166
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1671. The `HEAD` pointer stays the same.
1682. The `MERGE_HEAD` ref is set to point to the other branch head.
1693. Paths that merged cleanly are updated both in the index file and
ffb1a4be 170 in your working tree.
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1714. For conflicting paths, the index file records up to three
172 versions: stage 1 stores the version from the common ancestor,
173 stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
b1889c36 174 can inspect the stages with `git ls-files -u`). The working
29b802aa 175 tree files contain the result of the "merge" program; i.e. 3-way
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176 merge results with familiar conflict markers `<<<` `===` `>>>`.
1775. No other changes are made. In particular, the local
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178 modifications you had before you started merge will stay the
179 same and the index entries for them stay as they were,
180 i.e. matching `HEAD`.
181
ed4a6baa 182If you tried a merge which resulted in complex conflicts and
35d2fffd 183want to start over, you can recover with `git merge --abort`.
ed4a6baa 184
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185MERGING TAG
186-----------
187
188When merging an annotated (and possibly signed) tag, Git always
189creates a merge commit even if a fast-forward merge is possible, and
190the commit message template is prepared with the tag message.
191Additionally, if the tag is signed, the signature check is reported
192as a comment in the message template. See also linkgit:git-tag[1].
193
194When you want to just integrate with the work leading to the commit
195that happens to be tagged, e.g. synchronizing with an upstream
196release point, you may not want to make an unnecessary merge commit.
197
198In such a case, you can "unwrap" the tag yourself before feeding it
199to `git merge`, or pass `--ff-only` when you do not have any work on
200your own. e.g.
201
e45bda87 202----
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203git fetch origin
204git merge v1.2.3^0
205git merge --ff-only v1.2.3
e45bda87 206----
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207
208
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209HOW CONFLICTS ARE PRESENTED
210---------------------------
211
212During a merge, the working tree files are updated to reflect the result
213of the merge. Among the changes made to the common ancestor's version,
214non-overlapping ones (that is, you changed an area of the file while the
215other side left that area intact, or vice versa) are incorporated in the
216final result verbatim. When both sides made changes to the same area,
2de9b711 217however, Git cannot randomly pick one side over the other, and asks you to
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218resolve it by leaving what both sides did to that area.
219
2de9b711 220By default, Git uses the same style as the one used by the "merge" program
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221from the RCS suite to present such a conflicted hunk, like this:
222
223------------
224Here are lines that are either unchanged from the common
225ancestor, or cleanly resolved because only one side changed.
226<<<<<<< yours:sample.txt
227Conflict resolution is hard;
228let's go shopping.
229=======
230Git makes conflict resolution easy.
231>>>>>>> theirs:sample.txt
232And here is another line that is cleanly resolved or unmodified.
233------------
234
29b802aa 235The area where a pair of conflicting changes happened is marked with markers
dcb11263 236`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
29b802aa 237is typically your side, and the part afterwards is typically their side.
70a3f897 238
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239The default format does not show what the original said in the conflicting
240area. You cannot tell how many lines are deleted and replaced with
241Barbie's remark on your side. The only thing you can tell is that your
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242side wants to say it is hard and you'd prefer to go shopping, while the
243other side wants to claim it is easy.
244
da0005b8 245An alternative style can be used by setting the "merge.conflictStyle"
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246configuration variable to "diff3". In "diff3" style, the above conflict
247may look like this:
248
249------------
250Here are lines that are either unchanged from the common
251ancestor, or cleanly resolved because only one side changed.
252<<<<<<< yours:sample.txt
253Conflict resolution is hard;
254let's go shopping.
255|||||||
256Conflict resolution is hard.
257=======
258Git makes conflict resolution easy.
259>>>>>>> theirs:sample.txt
260And here is another line that is cleanly resolved or unmodified.
261------------
262
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263In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
264another `|||||||` marker that is followed by the original text. You can
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265tell that the original just stated a fact, and your side simply gave in to
266that statement and gave up, while the other side tried to have a more
267positive attitude. You can sometimes come up with a better resolution by
268viewing the original.
269
270
271HOW TO RESOLVE CONFLICTS
272------------------------
273
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274After seeing a conflict, you can do two things:
275
29b802aa 276 * Decide not to merge. The only clean-ups you need are to reset
ffb1a4be 277 the index file to the `HEAD` commit to reverse 2. and to clean
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278 up working tree changes made by 2. and 3.; `git merge --abort`
279 can be used for this.
ffb1a4be 280
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281 * Resolve the conflicts. Git will mark the conflicts in
282 the working tree. Edit the files into shape and
0b444cdb 283 'git add' them to the index. Use 'git commit' to seal the deal.
ffb1a4be 284
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285You can work through the conflict with a number of tools:
286
ca768288 287 * Use a mergetool. `git mergetool` to launch a graphical
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288 mergetool which will work you through the merge.
289
ca768288 290 * Look at the diffs. `git diff` will show a three-way diff,
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291 highlighting changes from both the `HEAD` and `MERGE_HEAD`
292 versions.
34ad1afa 293
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294 * Look at the diffs from each branch. `git log --merge -p <path>`
295 will show diffs first for the `HEAD` version and then the
296 `MERGE_HEAD` version.
34ad1afa 297
ca768288 298 * Look at the originals. `git show :1:filename` shows the
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299 common ancestor, `git show :2:filename` shows the `HEAD`
300 version, and `git show :3:filename` shows the `MERGE_HEAD`
301 version.
ffb1a4be 302
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303
304EXAMPLES
305--------
306
307* Merge branches `fixes` and `enhancements` on top of
308 the current branch, making an octopus merge:
309+
310------------------------------------------------
311$ git merge fixes enhancements
312------------------------------------------------
313
314* Merge branch `obsolete` into the current branch, using `ours`
315 merge strategy:
316+
317------------------------------------------------
318$ git merge -s ours obsolete
319------------------------------------------------
320
321* Merge branch `maint` into the current branch, but do not make
322 a new commit automatically:
323+
324------------------------------------------------
325$ git merge --no-commit maint
326------------------------------------------------
327+
328This can be used when you want to include further changes to the
329merge, or want to write your own merge commit message.
330+
331You should refrain from abusing this option to sneak substantial
332changes into a merge commit. Small fixups like bumping
333release/version name would be acceptable.
334
335
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336include::merge-strategies.txt[]
337
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338CONFIGURATION
339-------------
340include::merge-config.txt[]
341
da0005b8 342branch.<name>.mergeOptions::
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343 Sets default options for merging into branch <name>. The syntax and
344 supported options are the same as those of 'git merge', but option
345 values containing whitespace characters are currently not supported.
346
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347SEE ALSO
348--------
5162e697 349linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
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350linkgit:gitattributes[5],
351linkgit:git-reset[1],
352linkgit:git-diff[1], linkgit:git-ls-files[1],
353linkgit:git-add[1], linkgit:git-rm[1],
354linkgit:git-mergetool[1]
3c64314c 355
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356GIT
357---
9e1f0a85 358Part of the linkgit:git[1] suite