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]
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 uncommitted changes is
60 discouraged: while possible, it leaves 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).
72 If `--log` is specified, a shortlog of the commits being merged
73 will be appended to the specified message.
75 The 'git fmt-merge-msg' command can be
76 used to give a good default for automated 'git merge'
77 invocations.
79 --rerere-autoupdate::
80 --no-rerere-autoupdate::
81 Allow the rerere mechanism to update the index with the
82 result of auto-conflict resolution if possible.
84 --abort::
85 Abort the current conflict resolution process, and
86 try to reconstruct the pre-merge state.
87 +
88 If there were uncommitted worktree changes present when the merge
89 started, 'git merge --abort' will in some cases be unable to
90 reconstruct these changes. It is therefore recommended to always
91 commit or stash your changes before running 'git merge'.
92 +
93 'git merge --abort' is equivalent to 'git reset --merge' when
94 `MERGE_HEAD` is present.
96 <commit>...::
97 Commits, usually other branch heads, to merge into our branch.
98 You need at least one <commit>. Specifying more than one
99 <commit> obviously means you are trying an Octopus.
102 PRE-MERGE CHECKS
103 ----------------
105 Before applying outside changes, you should get your own work in
106 good shape and committed locally, so it will not be clobbered if
107 there are conflicts. See also linkgit:git-stash[1].
108 'git pull' and 'git merge' will stop without doing anything when
109 local uncommitted changes overlap with files that 'git pull'/'git
110 merge' may need to update.
112 To avoid recording unrelated changes in the merge commit,
113 'git pull' and 'git merge' will also abort if there are any changes
114 registered in the index relative to the `HEAD` commit. (One
115 exception is when the changed index entries are in the state that
116 would result from the merge already.)
118 If all named commits are already ancestors of `HEAD`, 'git merge'
119 will exit early with the message "Already up-to-date."
121 FAST-FORWARD MERGE
122 ------------------
124 Often the current branch head is an ancestor of the named commit.
125 This is the most common case especially when invoked from 'git
126 pull': you are tracking an upstream repository, you have committed
127 no local changes, and now you want to update to a newer upstream
128 revision. In this case, a new commit is not needed to store the
129 combined history; instead, the `HEAD` (along with the index) is
130 updated to point at the named commit, without creating an extra
131 merge commit.
133 This behavior can be suppressed with the `--no-ff` option.
135 TRUE MERGE
136 ----------
138 Except in a fast-forward merge (see above), the branches to be
139 merged must be tied together by a merge commit that has both of them
140 as its parents.
142 A merged version reconciling the changes from all branches to be
143 merged is committed, and your `HEAD`, index, and working tree are
144 updated to it. It is possible to have modifications in the working
145 tree as long as they do not overlap; the update will preserve them.
147 When it is not obvious how to reconcile the changes, the following
148 happens:
150 1. The `HEAD` pointer stays the same.
151 2. The `MERGE_HEAD` ref is set to point to the other branch head.
152 3. Paths that merged cleanly are updated both in the index file and
153 in your working tree.
154 4. For conflicting paths, the index file records up to three
155 versions: stage 1 stores the version from the common ancestor,
156 stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
157 can inspect the stages with `git ls-files -u`). The working
158 tree files contain the result of the "merge" program; i.e. 3-way
159 merge results with familiar conflict markers `<<<` `===` `>>>`.
160 5. No other changes are made. In particular, the local
161 modifications you had before you started merge will stay the
162 same and the index entries for them stay as they were,
163 i.e. matching `HEAD`.
165 If you tried a merge which resulted in complex conflicts and
166 want to start over, you can recover with `git merge --abort`.
168 HOW CONFLICTS ARE PRESENTED
169 ---------------------------
171 During a merge, the working tree files are updated to reflect the result
172 of the merge. Among the changes made to the common ancestor's version,
173 non-overlapping ones (that is, you changed an area of the file while the
174 other side left that area intact, or vice versa) are incorporated in the
175 final result verbatim. When both sides made changes to the same area,
176 however, git cannot randomly pick one side over the other, and asks you to
177 resolve it by leaving what both sides did to that area.
179 By default, git uses the same style as that is used by "merge" program
180 from the RCS suite to present such a conflicted hunk, like this:
182 ------------
183 Here are lines that are either unchanged from the common
184 ancestor, or cleanly resolved because only one side changed.
185 <<<<<<< yours:sample.txt
186 Conflict resolution is hard;
187 let's go shopping.
188 =======
189 Git makes conflict resolution easy.
190 >>>>>>> theirs:sample.txt
191 And here is another line that is cleanly resolved or unmodified.
192 ------------
194 The area where a pair of conflicting changes happened is marked with markers
195 `<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
196 is typically your side, and the part afterwards is typically their side.
198 The default format does not show what the original said in the conflicting
199 area. You cannot tell how many lines are deleted and replaced with
200 Barbie's remark on your side. The only thing you can tell is that your
201 side wants to say it is hard and you'd prefer to go shopping, while the
202 other side wants to claim it is easy.
204 An alternative style can be used by setting the "merge.conflictstyle"
205 configuration variable to "diff3". In "diff3" style, the above conflict
206 may look like this:
208 ------------
209 Here are lines that are either unchanged from the common
210 ancestor, or cleanly resolved because only one side changed.
211 <<<<<<< yours:sample.txt
212 Conflict resolution is hard;
213 let's go shopping.
214 |||||||
215 Conflict resolution is hard.
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 In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
223 another `|||||||` marker that is followed by the original text. You can
224 tell that the original just stated a fact, and your side simply gave in to
225 that statement and gave up, while the other side tried to have a more
226 positive attitude. You can sometimes come up with a better resolution by
227 viewing the original.
230 HOW TO RESOLVE CONFLICTS
231 ------------------------
233 After seeing a conflict, you can do two things:
235 * Decide not to merge. The only clean-ups you need are to reset
236 the index file to the `HEAD` commit to reverse 2. and to clean
237 up working tree changes made by 2. and 3.; `git merge --abort`
238 can be used for this.
240 * Resolve the conflicts. Git will mark the conflicts in
241 the working tree. Edit the files into shape and
242 'git add' them to the index. Use 'git commit' to seal the deal.
244 You can work through the conflict with a number of tools:
246 * Use a mergetool. `git mergetool` to launch a graphical
247 mergetool which will work you through the merge.
249 * Look at the diffs. `git diff` will show a three-way diff,
250 highlighting changes from both the `HEAD` and `MERGE_HEAD`
251 versions.
253 * Look at the diffs from each branch. `git log --merge -p <path>`
254 will show diffs first for the `HEAD` version and then the
255 `MERGE_HEAD` version.
257 * Look at the originals. `git show :1:filename` shows the
258 common ancestor, `git show :2:filename` shows the `HEAD`
259 version, and `git show :3:filename` shows the `MERGE_HEAD`
260 version.
263 EXAMPLES
264 --------
266 * Merge branches `fixes` and `enhancements` on top of
267 the current branch, making an octopus merge:
268 +
269 ------------------------------------------------
270 $ git merge fixes enhancements
271 ------------------------------------------------
273 * Merge branch `obsolete` into the current branch, using `ours`
274 merge strategy:
275 +
276 ------------------------------------------------
277 $ git merge -s ours obsolete
278 ------------------------------------------------
280 * Merge branch `maint` into the current branch, but do not make
281 a new commit automatically:
282 +
283 ------------------------------------------------
284 $ git merge --no-commit maint
285 ------------------------------------------------
286 +
287 This can be used when you want to include further changes to the
288 merge, or want to write your own merge commit message.
289 +
290 You should refrain from abusing this option to sneak substantial
291 changes into a merge commit. Small fixups like bumping
292 release/version name would be acceptable.
295 include::merge-strategies.txt[]
297 CONFIGURATION
298 -------------
299 include::merge-config.txt[]
301 branch.<name>.mergeoptions::
302 Sets default options for merging into branch <name>. The syntax and
303 supported options are the same as those of 'git merge', but option
304 values containing whitespace characters are currently not supported.
306 SEE ALSO
307 --------
308 linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
309 linkgit:gitattributes[5],
310 linkgit:git-reset[1],
311 linkgit:git-diff[1], linkgit:git-ls-files[1],
312 linkgit:git-add[1], linkgit:git-rm[1],
313 linkgit:git-mergetool[1]
315 Author
316 ------
317 Written by Junio C Hamano <gitster@pobox.com>
320 Documentation
321 --------------
322 Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
324 GIT
325 ---
326 Part of the linkgit:git[1] suite