Documentation: merge: move merge strategy list to end
[git/git.git] / Documentation / git-merge.txt
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1git-merge(1)
2============
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3
4NAME
5----
c3f0baac 6git-merge - Join two or more development histories together
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7
8
9SYNOPSIS
10--------
17bcdad3 11[verse]
b1889c36 12'git merge' [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]...
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13 [-m <msg>] <commit>...
14'git merge' <msg> HEAD <commit>...
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15
16DESCRIPTION
17-----------
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18Merges the history specified by <commit> into HEAD, optionally using a
19specific merge strategy.
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57bddb11 21The second syntax (<msg> `HEAD` <commit>...) is supported for
dee48c3c 22historical reasons. Do not use it from the command line or in
57bddb11 23new scripts. It is the same as `git merge -m <msg> <commit>...`.
dee48c3c 24
0b444cdb 25*Warning*: Running 'git merge' with uncommitted changes is
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26discouraged: while possible, it leaves you in a state that is hard to
27back out of in the case of a conflict.
28
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29
30OPTIONS
31-------
93d69d86 32include::merge-options.txt[]
0f69be53 33
dee48c3c 34-m <msg>::
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35 Set the commit message to be used for the merge commit (in
36 case one is created). The 'git fmt-merge-msg' command can be
37 used to give a good default for automated 'git merge'
38 invocations.
3c64314c 39
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40<commit>...::
41 Commits, usually other branch heads, to merge into our branch.
42 You need at least one <commit>. Specifying more than one
43 <commit> obviously means you are trying an Octopus.
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44
45
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46HOW MERGE WORKS
47---------------
48
49A merge is always between the current `HEAD` and one or more
81646ad2 50commits (usually, branch head or tag), and the index file must
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51match the tree of `HEAD` commit (i.e. the contents of the last commit)
52when it starts out. In other words, `git diff --cached HEAD` must
53report no changes. (One exception is when the changed index
54entries are already in the same state that would result from
55the merge anyway.)
56
57Three kinds of merge can happen:
58
59* The merged commit is already contained in `HEAD`. This is the
60 simplest case, called "Already up-to-date."
61
62* `HEAD` is already contained in the merged commit. This is the
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63 most common case especially when invoked from 'git pull':
64 you are tracking an upstream repository, have committed no local
c0be8aa0 65 changes and now you want to update to a newer upstream revision.
29b802aa 66 Your `HEAD` (and the index) is updated to point at the merged
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67 commit, without creating an extra merge commit. This is
68 called "Fast-forward".
69
70* Both the merged commit and `HEAD` are independent and must be
29b802aa 71 tied together by a merge commit that has both of them as its parents.
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72 The rest of this section describes this "True merge" case.
73
74The chosen merge strategy merges the two commits into a single
75new source tree.
29b802aa 76When things merge cleanly, this is what happens:
ffb1a4be 77
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781. The results are updated both in the index file and in your
79 working tree;
802. Index file is written out as a tree;
813. The tree gets committed; and
824. The `HEAD` pointer gets advanced.
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83
84Because of 2., we require that the original state of the index
29b802aa 85file matches exactly the current `HEAD` commit; otherwise we
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86will write out your local changes already registered in your
87index file along with the merge result, which is not good.
29b802aa 88Because 1. involves only those paths differing between your
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89branch and the branch you are merging
90(which is typically a fraction of the whole tree), you can
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91have local modifications in your working tree as long as they do
92not overlap with what the merge updates.
93
29b802aa 94When there are conflicts, the following happens:
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95
961. `HEAD` stays the same.
97
982. Cleanly merged paths are updated both in the index file and
99 in your working tree.
100
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1013. For conflicting paths, the index file records up to three
102 versions; stage1 stores the version from the common ancestor,
57bddb11 103 stage2 from `HEAD`, and stage3 from the other branch (you
b1889c36 104 can inspect the stages with `git ls-files -u`). The working
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105 tree files contain the result of the "merge" program; i.e. 3-way
106 merge results with familiar conflict markers `<<< === >>>`.
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107
1084. No other changes are done. In particular, the local
109 modifications you had before you started merge will stay the
110 same and the index entries for them stay as they were,
111 i.e. matching `HEAD`.
112
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113If you tried a merge which resulted in complex conflicts and
114want to start over, you can recover with `git reset --merge`.
115
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116HOW CONFLICTS ARE PRESENTED
117---------------------------
118
119During a merge, the working tree files are updated to reflect the result
120of the merge. Among the changes made to the common ancestor's version,
121non-overlapping ones (that is, you changed an area of the file while the
122other side left that area intact, or vice versa) are incorporated in the
123final result verbatim. When both sides made changes to the same area,
124however, git cannot randomly pick one side over the other, and asks you to
125resolve it by leaving what both sides did to that area.
126
127By default, git uses the same style as that is used by "merge" program
128from the RCS suite to present such a conflicted hunk, like this:
129
130------------
131Here are lines that are either unchanged from the common
132ancestor, or cleanly resolved because only one side changed.
133<<<<<<< yours:sample.txt
134Conflict resolution is hard;
135let's go shopping.
136=======
137Git makes conflict resolution easy.
138>>>>>>> theirs:sample.txt
139And here is another line that is cleanly resolved or unmodified.
140------------
141
29b802aa 142The area where a pair of conflicting changes happened is marked with markers
dcb11263 143`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
29b802aa 144is typically your side, and the part afterwards is typically their side.
70a3f897 145
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146The default format does not show what the original said in the conflicting
147area. You cannot tell how many lines are deleted and replaced with
148Barbie's remark on your side. The only thing you can tell is that your
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149side wants to say it is hard and you'd prefer to go shopping, while the
150other side wants to claim it is easy.
151
152An alternative style can be used by setting the "merge.conflictstyle"
153configuration variable to "diff3". In "diff3" style, the above conflict
154may look like this:
155
156------------
157Here are lines that are either unchanged from the common
158ancestor, or cleanly resolved because only one side changed.
159<<<<<<< yours:sample.txt
160Conflict resolution is hard;
161let's go shopping.
162|||||||
163Conflict resolution is hard.
164=======
165Git makes conflict resolution easy.
166>>>>>>> theirs:sample.txt
167And here is another line that is cleanly resolved or unmodified.
168------------
169
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170In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
171another `|||||||` marker that is followed by the original text. You can
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172tell that the original just stated a fact, and your side simply gave in to
173that statement and gave up, while the other side tried to have a more
174positive attitude. You can sometimes come up with a better resolution by
175viewing the original.
176
177
178HOW TO RESOLVE CONFLICTS
179------------------------
180
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181After seeing a conflict, you can do two things:
182
29b802aa 183 * Decide not to merge. The only clean-ups you need are to reset
ffb1a4be 184 the index file to the `HEAD` commit to reverse 2. and to clean
ca768288 185 up working tree changes made by 2. and 3.; `git-reset --hard` can
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186 be used for this.
187
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188 * Resolve the conflicts. Git will mark the conflicts in
189 the working tree. Edit the files into shape and
0b444cdb 190 'git add' them to the index. Use 'git commit' to seal the deal.
ffb1a4be 191
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192You can work through the conflict with a number of tools:
193
ca768288 194 * Use a mergetool. `git mergetool` to launch a graphical
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195 mergetool which will work you through the merge.
196
ca768288 197 * Look at the diffs. `git diff` will show a three-way diff,
57bddb11 198 highlighting changes from both the HEAD and their versions.
34ad1afa 199
ca768288 200 * Look at the diffs on their own. `git log --merge -p <path>`
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201 will show diffs first for the HEAD version and then
202 their version.
34ad1afa 203
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204 * Look at the originals. `git show :1:filename` shows the
205 common ancestor, `git show :2:filename` shows the HEAD
206 version and `git show :3:filename` shows their version.
ffb1a4be 207
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208
209EXAMPLES
210--------
211
212* Merge branches `fixes` and `enhancements` on top of
213 the current branch, making an octopus merge:
214+
215------------------------------------------------
216$ git merge fixes enhancements
217------------------------------------------------
218
219* Merge branch `obsolete` into the current branch, using `ours`
220 merge strategy:
221+
222------------------------------------------------
223$ git merge -s ours obsolete
224------------------------------------------------
225
226* Merge branch `maint` into the current branch, but do not make
227 a new commit automatically:
228+
229------------------------------------------------
230$ git merge --no-commit maint
231------------------------------------------------
232+
233This can be used when you want to include further changes to the
234merge, or want to write your own merge commit message.
235+
236You should refrain from abusing this option to sneak substantial
237changes into a merge commit. Small fixups like bumping
238release/version name would be acceptable.
239
240
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241include::merge-strategies.txt[]
242
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243CONFIGURATION
244-------------
245include::merge-config.txt[]
246
247branch.<name>.mergeoptions::
248 Sets default options for merging into branch <name>. The syntax and
249 supported options are the same as those of 'git merge', but option
250 values containing whitespace characters are currently not supported.
251
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252SEE ALSO
253--------
5162e697 254linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
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255linkgit:gitattributes[5],
256linkgit:git-reset[1],
257linkgit:git-diff[1], linkgit:git-ls-files[1],
258linkgit:git-add[1], linkgit:git-rm[1],
259linkgit:git-mergetool[1]
3c64314c 260
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261Author
262------
59eb68aa 263Written by Junio C Hamano <gitster@pobox.com>
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264
265
266Documentation
267--------------
268Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
269
270GIT
271---
9e1f0a85 272Part of the linkgit:git[1] suite