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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>] [-S[<key-id>]]
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. The automated message can include the branch description.
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, merge the remote-tracking
105 branches that the current branch is configured to use as its upstream.
106 See also the configuration section of this manual page.
107 +
108 When `FETCH_HEAD` (and no other commit) is specified, the branches
109 recorded in the `.git/FETCH_HEAD` file by the previous invocation
110 of `git fetch` for merging are merged to the current branch.
113 PRE-MERGE CHECKS
114 ----------------
116 Before applying outside changes, you should get your own work in
117 good shape and committed locally, so it will not be clobbered if
118 there are conflicts. See also linkgit:git-stash[1].
119 'git pull' and 'git merge' will stop without doing anything when
120 local uncommitted changes overlap with files that 'git pull'/'git
121 merge' may need to update.
123 To avoid recording unrelated changes in the merge commit,
124 'git pull' and 'git merge' will also abort if there are any changes
125 registered in the index relative to the `HEAD` commit. (One
126 exception is when the changed index entries are in the state that
127 would result from the merge already.)
129 If all named commits are already ancestors of `HEAD`, 'git merge'
130 will exit early with the message "Already up-to-date."
132 FAST-FORWARD MERGE
133 ------------------
135 Often the current branch head is an ancestor of the named commit.
136 This is the most common case especially when invoked from 'git
137 pull': you are tracking an upstream repository, you have committed
138 no local changes, and now you want to update to a newer upstream
139 revision. In this case, a new commit is not needed to store the
140 combined history; instead, the `HEAD` (along with the index) is
141 updated to point at the named commit, without creating an extra
142 merge commit.
144 This behavior can be suppressed with the `--no-ff` option.
146 TRUE MERGE
147 ----------
149 Except in a fast-forward merge (see above), the branches to be
150 merged must be tied together by a merge commit that has both of them
151 as its parents.
153 A merged version reconciling the changes from all branches to be
154 merged is committed, and your `HEAD`, index, and working tree are
155 updated to it. It is possible to have modifications in the working
156 tree as long as they do not overlap; the update will preserve them.
158 When it is not obvious how to reconcile the changes, the following
159 happens:
161 1. The `HEAD` pointer stays the same.
162 2. The `MERGE_HEAD` ref is set to point to the other branch head.
163 3. Paths that merged cleanly are updated both in the index file and
164 in your working tree.
165 4. For conflicting paths, the index file records up to three
166 versions: stage 1 stores the version from the common ancestor,
167 stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
168 can inspect the stages with `git ls-files -u`). The working
169 tree files contain the result of the "merge" program; i.e. 3-way
170 merge results with familiar conflict markers `<<<` `===` `>>>`.
171 5. No other changes are made. In particular, the local
172 modifications you had before you started merge will stay the
173 same and the index entries for them stay as they were,
174 i.e. matching `HEAD`.
176 If you tried a merge which resulted in complex conflicts and
177 want to start over, you can recover with `git merge --abort`.
179 MERGING TAG
180 -----------
182 When merging an annotated (and possibly signed) tag, Git always
183 creates a merge commit even if a fast-forward merge is possible, and
184 the commit message template is prepared with the tag message.
185 Additionally, if the tag is signed, the signature check is reported
186 as a comment in the message template. See also linkgit:git-tag[1].
188 When you want to just integrate with the work leading to the commit
189 that happens to be tagged, e.g. synchronizing with an upstream
190 release point, you may not want to make an unnecessary merge commit.
192 In such a case, you can "unwrap" the tag yourself before feeding it
193 to `git merge`, or pass `--ff-only` when you do not have any work on
194 your own. e.g.
196 ----
197 git fetch origin
198 git merge v1.2.3^0
199 git merge --ff-only v1.2.3
200 ----
203 HOW CONFLICTS ARE PRESENTED
204 ---------------------------
206 During a merge, the working tree files are updated to reflect the result
207 of the merge. Among the changes made to the common ancestor's version,
208 non-overlapping ones (that is, you changed an area of the file while the
209 other side left that area intact, or vice versa) are incorporated in the
210 final result verbatim. When both sides made changes to the same area,
211 however, Git cannot randomly pick one side over the other, and asks you to
212 resolve it by leaving what both sides did to that area.
214 By default, Git uses the same style as the one used by the "merge" program
215 from the RCS suite to present such a conflicted hunk, like this:
217 ------------
218 Here are lines that are either unchanged from the common
219 ancestor, or cleanly resolved because only one side changed.
220 <<<<<<< yours:sample.txt
221 Conflict resolution is hard;
222 let's go shopping.
223 =======
224 Git makes conflict resolution easy.
225 >>>>>>> theirs:sample.txt
226 And here is another line that is cleanly resolved or unmodified.
227 ------------
229 The area where a pair of conflicting changes happened is marked with markers
230 `<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
231 is typically your side, and the part afterwards is typically their side.
233 The default format does not show what the original said in the conflicting
234 area. You cannot tell how many lines are deleted and replaced with
235 Barbie's remark on your side. The only thing you can tell is that your
236 side wants to say it is hard and you'd prefer to go shopping, while the
237 other side wants to claim it is easy.
239 An alternative style can be used by setting the "merge.conflictStyle"
240 configuration variable to "diff3". In "diff3" style, the above conflict
241 may look like this:
243 ------------
244 Here are lines that are either unchanged from the common
245 ancestor, or cleanly resolved because only one side changed.
246 <<<<<<< yours:sample.txt
247 Conflict resolution is hard;
248 let's go shopping.
249 |||||||
250 Conflict resolution is hard.
251 =======
252 Git makes conflict resolution easy.
253 >>>>>>> theirs:sample.txt
254 And here is another line that is cleanly resolved or unmodified.
255 ------------
257 In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
258 another `|||||||` marker that is followed by the original text. You can
259 tell that the original just stated a fact, and your side simply gave in to
260 that statement and gave up, while the other side tried to have a more
261 positive attitude. You can sometimes come up with a better resolution by
262 viewing the original.
265 HOW TO RESOLVE CONFLICTS
266 ------------------------
268 After seeing a conflict, you can do two things:
270 * Decide not to merge. The only clean-ups you need are to reset
271 the index file to the `HEAD` commit to reverse 2. and to clean
272 up working tree changes made by 2. and 3.; `git merge --abort`
273 can be used for this.
275 * Resolve the conflicts. Git will mark the conflicts in
276 the working tree. Edit the files into shape and
277 'git add' them to the index. Use 'git commit' to seal the deal.
279 You can work through the conflict with a number of tools:
281 * Use a mergetool. `git mergetool` to launch a graphical
282 mergetool which will work you through the merge.
284 * Look at the diffs. `git diff` will show a three-way diff,
285 highlighting changes from both the `HEAD` and `MERGE_HEAD`
286 versions.
288 * Look at the diffs from each branch. `git log --merge -p <path>`
289 will show diffs first for the `HEAD` version and then the
290 `MERGE_HEAD` version.
292 * Look at the originals. `git show :1:filename` shows the
293 common ancestor, `git show :2:filename` shows the `HEAD`
294 version, and `git show :3:filename` shows the `MERGE_HEAD`
295 version.
298 EXAMPLES
299 --------
301 * Merge branches `fixes` and `enhancements` on top of
302 the current branch, making an octopus merge:
303 +
304 ------------------------------------------------
305 $ git merge fixes enhancements
306 ------------------------------------------------
308 * Merge branch `obsolete` into the current branch, using `ours`
309 merge strategy:
310 +
311 ------------------------------------------------
312 $ git merge -s ours obsolete
313 ------------------------------------------------
315 * Merge branch `maint` into the current branch, but do not make
316 a new commit automatically:
317 +
318 ------------------------------------------------
319 $ git merge --no-commit maint
320 ------------------------------------------------
321 +
322 This can be used when you want to include further changes to the
323 merge, or want to write your own merge commit message.
324 +
325 You should refrain from abusing this option to sneak substantial
326 changes into a merge commit. Small fixups like bumping
327 release/version name would be acceptable.
330 include::merge-strategies.txt[]
332 CONFIGURATION
333 -------------
334 include::merge-config.txt[]
336 branch.<name>.mergeOptions::
337 Sets default options for merging into branch <name>. The syntax and
338 supported options are the same as those of 'git merge', but option
339 values containing whitespace characters are currently not supported.
341 SEE ALSO
342 --------
343 linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
344 linkgit:gitattributes[5],
345 linkgit:git-reset[1],
346 linkgit:git-diff[1], linkgit:git-ls-files[1],
347 linkgit:git-add[1], linkgit:git-rm[1],
348 linkgit:git-mergetool[1]
350 GIT
351 ---
352 Part of the linkgit:git[1] suite