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