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0f69be53 JH |
1 | git-merge(1) |
2 | ============ | |
0f69be53 JH |
3 | |
4 | NAME | |
5 | ---- | |
c3f0baac | 6 | git-merge - Join two or more development histories together |
0f69be53 JH |
7 | |
8 | ||
9 | SYNOPSIS | |
10 | -------- | |
17bcdad3 | 11 | [verse] |
adda3c3b MB |
12 | 'git merge' [-n] [--stat] [--no-commit] [--squash] |
13 | [-s <strategy>] [-X <strategy-option>] | |
add0951a | 14 | [--[no-]rerere-autoupdate] [-m <msg>] <commit>... |
57bddb11 | 15 | 'git merge' <msg> HEAD <commit>... |
35d2fffd | 16 | 'git merge' --abort |
0f69be53 JH |
17 | |
18 | DESCRIPTION | |
19 | ----------- | |
b40bb374 JN |
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. | |
25 | ||
26 | Assume the following history exists and the current branch is | |
27 | "`master`": | |
28 | ||
29 | ------------ | |
30 | A---B---C topic | |
31 | / | |
32 | D---E---F---G master | |
33 | ------------ | |
34 | ||
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. | |
40 | ||
41 | ------------ | |
42 | A---B---C topic | |
43 | / \ | |
44 | D---E---F---G---H master | |
45 | ------------ | |
0f69be53 | 46 | |
57bddb11 | 47 | The second syntax (<msg> `HEAD` <commit>...) is supported for |
dee48c3c | 48 | historical reasons. Do not use it from the command line or in |
57bddb11 | 49 | new scripts. It is the same as `git merge -m <msg> <commit>...`. |
dee48c3c | 50 | |
35d2fffd JH |
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: | |
58 | ||
0b444cdb | 59 | *Warning*: Running 'git merge' with uncommitted changes is |
e330d8ca TR |
60 | discouraged: while possible, it leaves you in a state that is hard to |
61 | back out of in the case of a conflict. | |
dee48c3c | 62 | |
0f69be53 JH |
63 | |
64 | OPTIONS | |
65 | ------- | |
93d69d86 | 66 | include::merge-options.txt[] |
0f69be53 | 67 | |
dee48c3c | 68 | -m <msg>:: |
0f8a02c6 | 69 | Set the commit message to be used for the merge commit (in |
f0ecac2b | 70 | case one is created). |
af77aee9 NP |
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. | |
3c64314c | 78 | |
cb6020bb JH |
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. | |
83 | ||
35d2fffd JH |
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. | |
95 | ||
57bddb11 TR |
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. | |
0f69be53 | 100 | |
bb73d73c | 101 | |
30f2bade JN |
102 | PRE-MERGE CHECKS |
103 | ---------------- | |
0f69be53 | 104 | |
30f2bade JN |
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. | |
3ae854c3 | 111 | |
30f2bade JN |
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.) | |
dbddb714 | 117 | |
30f2bade JN |
118 | If all named commits are already ancestors of `HEAD`, 'git merge' |
119 | will exit early with the message "Already up-to-date." | |
3ae854c3 | 120 | |
29280311 JN |
121 | FAST-FORWARD MERGE |
122 | ------------------ | |
123 | ||
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. | |
132 | ||
133 | This behavior can be suppressed with the `--no-ff` option. | |
ffb1a4be | 134 | |
ebef7e50 JN |
135 | TRUE MERGE |
136 | ---------- | |
c0be8aa0 | 137 | |
29280311 JN |
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. | |
ffb1a4be | 141 | |
ebef7e50 JN |
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. | |
ffb1a4be | 146 | |
ebef7e50 JN |
147 | When it is not obvious how to reconcile the changes, the following |
148 | happens: | |
ffb1a4be | 149 | |
ebef7e50 JN |
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 | |
ffb1a4be | 153 | in your working tree. |
ebef7e50 JN |
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 | |
b1889c36 | 157 | can inspect the stages with `git ls-files -u`). The working |
29b802aa | 158 | tree files contain the result of the "merge" program; i.e. 3-way |
ebef7e50 JN |
159 | merge results with familiar conflict markers `<<<` `===` `>>>`. |
160 | 5. No other changes are made. In particular, the local | |
ffb1a4be JH |
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`. | |
164 | ||
ed4a6baa | 165 | If you tried a merge which resulted in complex conflicts and |
35d2fffd | 166 | want to start over, you can recover with `git merge --abort`. |
ed4a6baa | 167 | |
70a3f897 JH |
168 | HOW CONFLICTS ARE PRESENTED |
169 | --------------------------- | |
170 | ||
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. | |
178 | ||
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: | |
181 | ||
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 | ------------ | |
193 | ||
29b802aa | 194 | The area where a pair of conflicting changes happened is marked with markers |
dcb11263 | 195 | `<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======` |
29b802aa | 196 | is typically your side, and the part afterwards is typically their side. |
70a3f897 | 197 | |
29b802aa RW |
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 | |
70a3f897 JH |
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. | |
203 | ||
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: | |
207 | ||
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 | ------------ | |
221 | ||
dcb11263 CJ |
222 | In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses |
223 | another `|||||||` marker that is followed by the original text. You can | |
70a3f897 JH |
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. | |
228 | ||
229 | ||
230 | HOW TO RESOLVE CONFLICTS | |
231 | ------------------------ | |
232 | ||
ffb1a4be JH |
233 | After seeing a conflict, you can do two things: |
234 | ||
29b802aa | 235 | * Decide not to merge. The only clean-ups you need are to reset |
ffb1a4be | 236 | the index file to the `HEAD` commit to reverse 2. and to clean |
35d2fffd JH |
237 | up working tree changes made by 2. and 3.; `git merge --abort` |
238 | can be used for this. | |
ffb1a4be | 239 | |
34ad1afa DH |
240 | * Resolve the conflicts. Git will mark the conflicts in |
241 | the working tree. Edit the files into shape and | |
0b444cdb | 242 | 'git add' them to the index. Use 'git commit' to seal the deal. |
ffb1a4be | 243 | |
34ad1afa DH |
244 | You can work through the conflict with a number of tools: |
245 | ||
ca768288 | 246 | * Use a mergetool. `git mergetool` to launch a graphical |
34ad1afa DH |
247 | mergetool which will work you through the merge. |
248 | ||
ca768288 | 249 | * Look at the diffs. `git diff` will show a three-way diff, |
3588cf94 JN |
250 | highlighting changes from both the `HEAD` and `MERGE_HEAD` |
251 | versions. | |
34ad1afa | 252 | |
3588cf94 JN |
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. | |
34ad1afa | 256 | |
ca768288 | 257 | * Look at the originals. `git show :1:filename` shows the |
3588cf94 JN |
258 | common ancestor, `git show :2:filename` shows the `HEAD` |
259 | version, and `git show :3:filename` shows the `MERGE_HEAD` | |
260 | version. | |
ffb1a4be | 261 | |
d504f697 CB |
262 | |
263 | EXAMPLES | |
264 | -------- | |
265 | ||
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 | ------------------------------------------------ | |
272 | ||
273 | * Merge branch `obsolete` into the current branch, using `ours` | |
274 | merge strategy: | |
275 | + | |
276 | ------------------------------------------------ | |
277 | $ git merge -s ours obsolete | |
278 | ------------------------------------------------ | |
279 | ||
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. | |
293 | ||
294 | ||
a4081bac JN |
295 | include::merge-strategies.txt[] |
296 | ||
35e9d630 JN |
297 | CONFIGURATION |
298 | ------------- | |
299 | include::merge-config.txt[] | |
300 | ||
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. | |
305 | ||
3c64314c PB |
306 | SEE ALSO |
307 | -------- | |
5162e697 | 308 | linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], |
483bc4f0 JN |
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] | |
3c64314c | 314 | |
0f69be53 JH |
315 | Author |
316 | ------ | |
59eb68aa | 317 | Written by Junio C Hamano <gitster@pobox.com> |
0f69be53 JH |
318 | |
319 | ||
320 | Documentation | |
321 | -------------- | |
322 | Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. | |
323 | ||
324 | GIT | |
325 | --- | |
9e1f0a85 | 326 | Part of the linkgit:git[1] suite |