pull: pass --signoff/--no-signoff to "git merge"
[git/git.git] / Documentation / git-merge.txt
1 git-merge(1)
2 ============
3
4 NAME
5 ----
6 git-merge - Join two or more development histories together
7
8
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-]allow-unrelated-histories]
15 [--[no-]rerere-autoupdate] [-m <msg>] [<commit>...]
16 'git merge' --abort
17 'git merge' --continue
18
19 DESCRIPTION
20 -----------
21 Incorporates changes from the named commits (since the time their
22 histories diverged from the current branch) into the current
23 branch. This command is used by 'git pull' to incorporate changes
24 from another repository and can be used by hand to merge changes
25 from one branch into another.
26
27 Assume 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
36 Then "`git merge topic`" will replay the changes made on the
37 `topic` branch since it diverged from `master` (i.e., `E`) until
38 its current commit (`C`) on top of `master`, and record the result
39 in a new commit along with the names of the two parent commits and
40 a log message from the user describing the changes.
41
42 ------------
43 A---B---C topic
44 / \
45 D---E---F---G---H master
46 ------------
47
48 The second syntax ("`git merge --abort`") can only be run after the
49 merge has resulted in conflicts. 'git merge --abort' will abort the
50 merge process and try to reconstruct the pre-merge state. However,
51 if there were uncommitted changes when the merge started (and
52 especially if those changes were further modified after the merge
53 was started), 'git merge --abort' will in some cases be unable to
54 reconstruct the original (pre-merge) changes. Therefore:
55
56 *Warning*: Running 'git merge' with non-trivial uncommitted changes is
57 discouraged: while possible, it may leave you in a state that is hard to
58 back out of in the case of a conflict.
59
60 The fourth syntax ("`git merge --continue`") can only be run after the
61 merge has resulted in conflicts.
62
63 OPTIONS
64 -------
65 include::merge-options.txt[]
66
67 -S[<keyid>]::
68 --gpg-sign[=<keyid>]::
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.
72
73 -m <msg>::
74 Set the commit message to be used for the merge commit (in
75 case one is created).
76 +
77 If `--log` is specified, a shortlog of the commits being merged
78 will be appended to the specified message.
79 +
80 The 'git fmt-merge-msg' command can be
81 used to give a good default for automated 'git merge'
82 invocations. The automated message can include the branch description.
83
84 --[no-]rerere-autoupdate::
85 Allow the rerere mechanism to update the index with the
86 result of auto-conflict resolution if possible.
87
88 --abort::
89 Abort the current conflict resolution process, and
90 try to reconstruct the pre-merge state.
91 +
92 If there were uncommitted worktree changes present when the merge
93 started, 'git merge --abort' will in some cases be unable to
94 reconstruct these changes. It is therefore recommended to always
95 commit 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
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
105 <commit>...::
106 Commits, usually other branch heads, to merge into our branch.
107 Specifying more than one commit will create a merge with
108 more than two parents (affectionately called an Octopus merge).
109 +
110 If no commit is given from the command line, merge the remote-tracking
111 branches that the current branch is configured to use as its upstream.
112 See also the configuration section of this manual page.
113 +
114 When `FETCH_HEAD` (and no other commit) is specified, the branches
115 recorded in the `.git/FETCH_HEAD` file by the previous invocation
116 of `git fetch` for merging are merged to the current branch.
117
118
119 PRE-MERGE CHECKS
120 ----------------
121
122 Before applying outside changes, you should get your own work in
123 good shape and committed locally, so it will not be clobbered if
124 there are conflicts. See also linkgit:git-stash[1].
125 'git pull' and 'git merge' will stop without doing anything when
126 local uncommitted changes overlap with files that 'git pull'/'git
127 merge' may need to update.
128
129 To avoid recording unrelated changes in the merge commit,
130 'git pull' and 'git merge' will also abort if there are any changes
131 registered in the index relative to the `HEAD` commit. (One
132 exception is when the changed index entries are in the state that
133 would result from the merge already.)
134
135 If all named commits are already ancestors of `HEAD`, 'git merge'
136 will exit early with the message "Already up to date."
137
138 FAST-FORWARD MERGE
139 ------------------
140
141 Often the current branch head is an ancestor of the named commit.
142 This is the most common case especially when invoked from 'git
143 pull': you are tracking an upstream repository, you have committed
144 no local changes, and now you want to update to a newer upstream
145 revision. In this case, a new commit is not needed to store the
146 combined history; instead, the `HEAD` (along with the index) is
147 updated to point at the named commit, without creating an extra
148 merge commit.
149
150 This behavior can be suppressed with the `--no-ff` option.
151
152 TRUE MERGE
153 ----------
154
155 Except in a fast-forward merge (see above), the branches to be
156 merged must be tied together by a merge commit that has both of them
157 as its parents.
158
159 A merged version reconciling the changes from all branches to be
160 merged is committed, and your `HEAD`, index, and working tree are
161 updated to it. It is possible to have modifications in the working
162 tree as long as they do not overlap; the update will preserve them.
163
164 When it is not obvious how to reconcile the changes, the following
165 happens:
166
167 1. The `HEAD` pointer stays the same.
168 2. The `MERGE_HEAD` ref is set to point to the other branch head.
169 3. Paths that merged cleanly are updated both in the index file and
170 in your working tree.
171 4. 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
174 can inspect the stages with `git ls-files -u`). The working
175 tree files contain the result of the "merge" program; i.e. 3-way
176 merge results with familiar conflict markers `<<<` `===` `>>>`.
177 5. No other changes are made. In particular, the local
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
182 If you tried a merge which resulted in complex conflicts and
183 want to start over, you can recover with `git merge --abort`.
184
185 MERGING TAG
186 -----------
187
188 When merging an annotated (and possibly signed) tag, Git always
189 creates a merge commit even if a fast-forward merge is possible, and
190 the commit message template is prepared with the tag message.
191 Additionally, if the tag is signed, the signature check is reported
192 as a comment in the message template. See also linkgit:git-tag[1].
193
194 When you want to just integrate with the work leading to the commit
195 that happens to be tagged, e.g. synchronizing with an upstream
196 release point, you may not want to make an unnecessary merge commit.
197
198 In such a case, you can "unwrap" the tag yourself before feeding it
199 to `git merge`, or pass `--ff-only` when you do not have any work on
200 your own. e.g.
201
202 ----
203 git fetch origin
204 git merge v1.2.3^0
205 git merge --ff-only v1.2.3
206 ----
207
208
209 HOW CONFLICTS ARE PRESENTED
210 ---------------------------
211
212 During a merge, the working tree files are updated to reflect the result
213 of the merge. Among the changes made to the common ancestor's version,
214 non-overlapping ones (that is, you changed an area of the file while the
215 other side left that area intact, or vice versa) are incorporated in the
216 final result verbatim. When both sides made changes to the same area,
217 however, Git cannot randomly pick one side over the other, and asks you to
218 resolve it by leaving what both sides did to that area.
219
220 By default, Git uses the same style as the one used by the "merge" program
221 from the RCS suite to present such a conflicted hunk, like this:
222
223 ------------
224 Here are lines that are either unchanged from the common
225 ancestor, or cleanly resolved because only one side changed.
226 <<<<<<< yours:sample.txt
227 Conflict resolution is hard;
228 let's go shopping.
229 =======
230 Git makes conflict resolution easy.
231 >>>>>>> theirs:sample.txt
232 And here is another line that is cleanly resolved or unmodified.
233 ------------
234
235 The area where a pair of conflicting changes happened is marked with markers
236 `<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
237 is typically your side, and the part afterwards is typically their side.
238
239 The default format does not show what the original said in the conflicting
240 area. You cannot tell how many lines are deleted and replaced with
241 Barbie's remark on your side. The only thing you can tell is that your
242 side wants to say it is hard and you'd prefer to go shopping, while the
243 other side wants to claim it is easy.
244
245 An alternative style can be used by setting the "merge.conflictStyle"
246 configuration variable to "diff3". In "diff3" style, the above conflict
247 may look like this:
248
249 ------------
250 Here are lines that are either unchanged from the common
251 ancestor, or cleanly resolved because only one side changed.
252 <<<<<<< yours:sample.txt
253 Conflict resolution is hard;
254 let's go shopping.
255 |||||||
256 Conflict resolution is hard.
257 =======
258 Git makes conflict resolution easy.
259 >>>>>>> theirs:sample.txt
260 And here is another line that is cleanly resolved or unmodified.
261 ------------
262
263 In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
264 another `|||||||` marker that is followed by the original text. You can
265 tell that the original just stated a fact, and your side simply gave in to
266 that statement and gave up, while the other side tried to have a more
267 positive attitude. You can sometimes come up with a better resolution by
268 viewing the original.
269
270
271 HOW TO RESOLVE CONFLICTS
272 ------------------------
273
274 After seeing a conflict, you can do two things:
275
276 * Decide not to merge. The only clean-ups you need are to reset
277 the index file to the `HEAD` commit to reverse 2. and to clean
278 up working tree changes made by 2. and 3.; `git merge --abort`
279 can be used for this.
280
281 * Resolve the conflicts. Git will mark the conflicts in
282 the working tree. Edit the files into shape and
283 'git add' them to the index. Use 'git commit' or
284 'git merge --continue' to seal the deal. The latter command
285 checks whether there is a (interrupted) merge in progress
286 before calling 'git commit'.
287
288 You can work through the conflict with a number of tools:
289
290 * Use a mergetool. `git mergetool` to launch a graphical
291 mergetool which will work you through the merge.
292
293 * Look at the diffs. `git diff` will show a three-way diff,
294 highlighting changes from both the `HEAD` and `MERGE_HEAD`
295 versions.
296
297 * Look at the diffs from each branch. `git log --merge -p <path>`
298 will show diffs first for the `HEAD` version and then the
299 `MERGE_HEAD` version.
300
301 * Look at the originals. `git show :1:filename` shows the
302 common ancestor, `git show :2:filename` shows the `HEAD`
303 version, and `git show :3:filename` shows the `MERGE_HEAD`
304 version.
305
306
307 EXAMPLES
308 --------
309
310 * Merge branches `fixes` and `enhancements` on top of
311 the current branch, making an octopus merge:
312 +
313 ------------------------------------------------
314 $ git merge fixes enhancements
315 ------------------------------------------------
316
317 * Merge branch `obsolete` into the current branch, using `ours`
318 merge strategy:
319 +
320 ------------------------------------------------
321 $ git merge -s ours obsolete
322 ------------------------------------------------
323
324 * Merge branch `maint` into the current branch, but do not make
325 a new commit automatically:
326 +
327 ------------------------------------------------
328 $ git merge --no-commit maint
329 ------------------------------------------------
330 +
331 This can be used when you want to include further changes to the
332 merge, or want to write your own merge commit message.
333 +
334 You should refrain from abusing this option to sneak substantial
335 changes into a merge commit. Small fixups like bumping
336 release/version name would be acceptable.
337
338
339 include::merge-strategies.txt[]
340
341 CONFIGURATION
342 -------------
343 include::merge-config.txt[]
344
345 branch.<name>.mergeOptions::
346 Sets default options for merging into branch <name>. The syntax and
347 supported options are the same as those of 'git merge', but option
348 values containing whitespace characters are currently not supported.
349
350 SEE ALSO
351 --------
352 linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
353 linkgit:gitattributes[5],
354 linkgit:git-reset[1],
355 linkgit:git-diff[1], linkgit:git-ls-files[1],
356 linkgit:git-add[1], linkgit:git-rm[1],
357 linkgit:git-mergetool[1]
358
359 GIT
360 ---
361 Part of the linkgit:git[1] suite