| blob | 439545926ecdcf609c299ca0e5ea44032969c1be |
1 git-merge(1)
2 ============
4 NAME
5 ----
6 git-merge - Join two or more development histories together
9 SYNOPSIS
10 --------
11 [verse]
12 'git merge' [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
13 [-s <strategy>] [-X <strategy-option>] [-S[<keyid>]]
14 [--[no-]rerere-autoupdate] [-m <msg>] [<commit>...]
15 'git merge' <msg> HEAD <commit>...
16 'git merge' --abort
18 DESCRIPTION
19 -----------
20 Incorporates changes from the named commits (since the time their
21 histories diverged from the current branch) into the current
22 branch. This command is used by 'git pull' to incorporate changes
23 from another repository and can be used by hand to merge changes
24 from one branch into another.
26 Assume the following history exists and the current branch is
27 "`master`":
29 ------------
30 A---B---C topic
31 /
32 D---E---F---G master
33 ------------
35 Then "`git merge topic`" will replay the changes made on the
36 `topic` branch since it diverged from `master` (i.e., `E`) until
37 its current commit (`C`) on top of `master`, and record the result
38 in a new commit along with the names of the two parent commits and
39 a log message from the user describing the changes.
41 ------------
42 A---B---C topic
43 / \
44 D---E---F---G---H master
45 ------------
47 The second syntax (<msg> `HEAD` <commit>...) is supported for
48 historical reasons. Do not use it from the command line or in
49 new scripts. It is the same as `git merge -m <msg> <commit>...`.
51 The third syntax ("`git merge --abort`") can only be run after the
52 merge has resulted in conflicts. 'git merge --abort' will abort the
53 merge process and try to reconstruct the pre-merge state. However,
54 if there were uncommitted changes when the merge started (and
55 especially if those changes were further modified after the merge
56 was started), 'git merge --abort' will in some cases be unable to
57 reconstruct the original (pre-merge) changes. Therefore:
59 *Warning*: Running 'git merge' with non-trivial uncommitted changes is
60 discouraged: while possible, it may leave you in a state that is hard to
61 back out of in the case of a conflict.
64 OPTIONS
65 -------
66 include::merge-options.txt[]
68 -S[<keyid>]::
69 --gpg-sign[=<keyid>]::
70 GPG-sign the resulting merge commit.
72 -m <msg>::
73 Set the commit message to be used for the merge commit (in
74 case one is created).
75 +
76 If `--log` is specified, a shortlog of the commits being merged
77 will be appended to the specified message.
78 +
79 The 'git fmt-merge-msg' command can be
80 used to give a good default for automated 'git merge'
81 invocations.
83 --[no-]rerere-autoupdate::
84 Allow the rerere mechanism to update the index with the
85 result of auto-conflict resolution if possible.
87 --abort::
88 Abort the current conflict resolution process, and
89 try to reconstruct the pre-merge state.
90 +
91 If there were uncommitted worktree changes present when the merge
92 started, 'git merge --abort' will in some cases be unable to
93 reconstruct these changes. It is therefore recommended to always
94 commit or stash your changes before running 'git merge'.
95 +
96 'git merge --abort' is equivalent to 'git reset --merge' when
97 `MERGE_HEAD` is present.
99 <commit>...::
100 Commits, usually other branch heads, to merge into our branch.
101 Specifying more than one commit will create a merge with
102 more than two parents (affectionately called an Octopus merge).
103 +
104 If no commit is given from the command line, and if `merge.defaultToUpstream`
105 configuration variable is set, merge the remote-tracking branches
106 that the current branch is configured to use as its upstream.
107 See also the configuration section of this manual page.
110 PRE-MERGE CHECKS
111 ----------------
113 Before applying outside changes, you should get your own work in
114 good shape and committed locally, so it will not be clobbered if
115 there are conflicts. See also linkgit:git-stash[1].
116 'git pull' and 'git merge' will stop without doing anything when
117 local uncommitted changes overlap with files that 'git pull'/'git
118 merge' may need to update.
120 To avoid recording unrelated changes in the merge commit,
121 'git pull' and 'git merge' will also abort if there are any changes
122 registered in the index relative to the `HEAD` commit. (One
123 exception is when the changed index entries are in the state that
124 would result from the merge already.)
126 If all named commits are already ancestors of `HEAD`, 'git merge'
127 will exit early with the message "Already up-to-date."
129 FAST-FORWARD MERGE
130 ------------------
132 Often the current branch head is an ancestor of the named commit.
133 This is the most common case especially when invoked from 'git
134 pull': you are tracking an upstream repository, you have committed
135 no local changes, and now you want to update to a newer upstream
136 revision. In this case, a new commit is not needed to store the
137 combined history; instead, the `HEAD` (along with the index) is
138 updated to point at the named commit, without creating an extra
139 merge commit.
141 This behavior can be suppressed with the `--no-ff` option.
143 TRUE MERGE
144 ----------
146 Except in a fast-forward merge (see above), the branches to be
147 merged must be tied together by a merge commit that has both of them
148 as its parents.
150 A merged version reconciling the changes from all branches to be
151 merged is committed, and your `HEAD`, index, and working tree are
152 updated to it. It is possible to have modifications in the working
153 tree as long as they do not overlap; the update will preserve them.
155 When it is not obvious how to reconcile the changes, the following
156 happens:
158 1. The `HEAD` pointer stays the same.
159 2. The `MERGE_HEAD` ref is set to point to the other branch head.
160 3. Paths that merged cleanly are updated both in the index file and
161 in your working tree.
162 4. For conflicting paths, the index file records up to three
163 versions: stage 1 stores the version from the common ancestor,
164 stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
165 can inspect the stages with `git ls-files -u`). The working
166 tree files contain the result of the "merge" program; i.e. 3-way
167 merge results with familiar conflict markers `<<<` `===` `>>>`.
168 5. No other changes are made. In particular, the local
169 modifications you had before you started merge will stay the
170 same and the index entries for them stay as they were,
171 i.e. matching `HEAD`.
173 If you tried a merge which resulted in complex conflicts and
174 want to start over, you can recover with `git merge --abort`.
176 MERGING TAG
177 -----------
179 When merging an annotated (and possibly signed) tag, Git always
180 creates a merge commit even if a fast-forward merge is possible, and
181 the commit message template is prepared with the tag message.
182 Additionally, if the tag is signed, the signature check is reported
183 as a comment in the message template. See also linkgit:git-tag[1].
185 When you want to just integrate with the work leading to the commit
186 that happens to be tagged, e.g. synchronizing with an upstream
187 release point, you may not want to make an unnecessary merge commit.
189 In such a case, you can "unwrap" the tag yourself before feeding it
190 to `git merge`, or pass `--ff-only` when you do not have any work on
191 your own. e.g.
193 ----
194 git fetch origin
195 git merge v1.2.3^0
196 git merge --ff-only v1.2.3
197 ----
200 HOW CONFLICTS ARE PRESENTED
201 ---------------------------
203 During a merge, the working tree files are updated to reflect the result
204 of the merge. Among the changes made to the common ancestor's version,
205 non-overlapping ones (that is, you changed an area of the file while the
206 other side left that area intact, or vice versa) are incorporated in the
207 final result verbatim. When both sides made changes to the same area,
208 however, Git cannot randomly pick one side over the other, and asks you to
209 resolve it by leaving what both sides did to that area.
211 By default, Git uses the same style as the one used by the "merge" program
212 from the RCS suite to present such a conflicted hunk, like this:
214 ------------
215 Here are lines that are either unchanged from the common
216 ancestor, or cleanly resolved because only one side changed.
217 <<<<<<< yours:sample.txt
218 Conflict resolution is hard;
219 let's go shopping.
220 =======
221 Git makes conflict resolution easy.
222 >>>>>>> theirs:sample.txt
223 And here is another line that is cleanly resolved or unmodified.
224 ------------
226 The area where a pair of conflicting changes happened is marked with markers
227 `<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
228 is typically your side, and the part afterwards is typically their side.
230 The default format does not show what the original said in the conflicting
231 area. You cannot tell how many lines are deleted and replaced with
232 Barbie's remark on your side. The only thing you can tell is that your
233 side wants to say it is hard and you'd prefer to go shopping, while the
234 other side wants to claim it is easy.
236 An alternative style can be used by setting the "merge.conflictstyle"
237 configuration variable to "diff3". In "diff3" style, the above conflict
238 may look like this:
240 ------------
241 Here are lines that are either unchanged from the common
242 ancestor, or cleanly resolved because only one side changed.
243 <<<<<<< yours:sample.txt
244 Conflict resolution is hard;
245 let's go shopping.
246 |||||||
247 Conflict resolution is hard.
248 =======
249 Git makes conflict resolution easy.
250 >>>>>>> theirs:sample.txt
251 And here is another line that is cleanly resolved or unmodified.
252 ------------
254 In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
255 another `|||||||` marker that is followed by the original text. You can
256 tell that the original just stated a fact, and your side simply gave in to
257 that statement and gave up, while the other side tried to have a more
258 positive attitude. You can sometimes come up with a better resolution by
259 viewing the original.
262 HOW TO RESOLVE CONFLICTS
263 ------------------------
265 After seeing a conflict, you can do two things:
267 * Decide not to merge. The only clean-ups you need are to reset
268 the index file to the `HEAD` commit to reverse 2. and to clean
269 up working tree changes made by 2. and 3.; `git merge --abort`
270 can be used for this.
272 * Resolve the conflicts. Git will mark the conflicts in
273 the working tree. Edit the files into shape and
274 'git add' them to the index. Use 'git commit' to seal the deal.
276 You can work through the conflict with a number of tools:
278 * Use a mergetool. `git mergetool` to launch a graphical
279 mergetool which will work you through the merge.
281 * Look at the diffs. `git diff` will show a three-way diff,
282 highlighting changes from both the `HEAD` and `MERGE_HEAD`
283 versions.
285 * Look at the diffs from each branch. `git log --merge -p <path>`
286 will show diffs first for the `HEAD` version and then the
287 `MERGE_HEAD` version.
289 * Look at the originals. `git show :1:filename` shows the
290 common ancestor, `git show :2:filename` shows the `HEAD`
291 version, and `git show :3:filename` shows the `MERGE_HEAD`
292 version.
295 EXAMPLES
296 --------
298 * Merge branches `fixes` and `enhancements` on top of
299 the current branch, making an octopus merge:
300 +
301 ------------------------------------------------
302 $ git merge fixes enhancements
303 ------------------------------------------------
305 * Merge branch `obsolete` into the current branch, using `ours`
306 merge strategy:
307 +
308 ------------------------------------------------
309 $ git merge -s ours obsolete
310 ------------------------------------------------
312 * Merge branch `maint` into the current branch, but do not make
313 a new commit automatically:
314 +
315 ------------------------------------------------
316 $ git merge --no-commit maint
317 ------------------------------------------------
318 +
319 This can be used when you want to include further changes to the
320 merge, or want to write your own merge commit message.
321 +
322 You should refrain from abusing this option to sneak substantial
323 changes into a merge commit. Small fixups like bumping
324 release/version name would be acceptable.
327 include::merge-strategies.txt[]
329 CONFIGURATION
330 -------------
331 include::merge-config.txt[]
333 branch.<name>.mergeoptions::
334 Sets default options for merging into branch <name>. The syntax and
335 supported options are the same as those of 'git merge', but option
336 values containing whitespace characters are currently not supported.
338 SEE ALSO
339 --------
340 linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
341 linkgit:gitattributes[5],
342 linkgit:git-reset[1],
343 linkgit:git-diff[1], linkgit:git-ls-files[1],
344 linkgit:git-add[1], linkgit:git-rm[1],
345 linkgit:git-mergetool[1]
347 GIT
348 ---
349 Part of the linkgit:git[1] suite