1git-merge(1) 2============ 3 4NAME 5---- 6git-merge - Join two or more development histories together 7 8 9SYNOPSIS 10-------- 11[verse] 12'git merge' [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]... 13 [-m <msg>] <commit>... 14'git merge' <msg> HEAD <commit>... 15 16DESCRIPTION 17----------- 18Incorporates changes from the named commits (since the time their 19histories diverged from the current branch) into the current 20branch. This command is used by 'git pull' to incorporate changes 21from another repository and can be used by hand to merge changes 22from one branch into another. 23 24Assume the following history exists and the current branch is 25"`master`": 26 27------------ 28 A---B---C topic 29 / 30 D---E---F---G master 31------------ 32 33Then "`git merge topic`" will replay the changes made on the 34`topic` branch since it diverged from `master` (i.e., `E`) until 35its current commit (`C`) on top of `master`, and record the result 36in a new commit along with the names of the two parent commits and 37a log message from the user describing the changes. 38 39------------ 40 A---B---C topic 41 / \ 42 D---E---F---G---H master 43------------ 44 45The second syntax (<msg> `HEAD` <commit>...) is supported for 46historical reasons. Do not use it from the command line or in 47new scripts. It is the same as `git merge -m <msg> <commit>...`. 48 49*Warning*: Running 'git merge' with uncommitted changes is 50discouraged: while possible, it leaves you in a state that is hard to 51back out of in the case of a conflict. 52 53 54OPTIONS 55------- 56include::merge-options.txt[] 57 58-m <msg>:: 59 Set the commit message to be used for the merge commit (in 60 case one is created). The 'git fmt-merge-msg' command can be 61 used to give a good default for automated 'git merge' 62 invocations. 63 64<commit>...:: 65 Commits, usually other branch heads, to merge into our branch. 66 You need at least one <commit>. Specifying more than one 67 <commit> obviously means you are trying an Octopus. 68 69 70PRE-MERGE CHECKS 71---------------- 72 73Before applying outside changes, you should get your own work in 74good shape and committed locally, so it will not be clobbered if 75there are conflicts. See also linkgit:git-stash[1]. 76'git pull' and 'git merge' will stop without doing anything when 77local uncommitted changes overlap with files that 'git pull'/'git 78merge' may need to update. 79 80To avoid recording unrelated changes in the merge commit, 81'git pull' and 'git merge' will also abort if there are any changes 82registered in the index relative to the `HEAD` commit. (One 83exception is when the changed index entries are in the state that 84would result from the merge already.) 85 86If all named commits are already ancestors of `HEAD`, 'git merge' 87will exit early with the message "Already up-to-date." 88 89FAST-FORWARD MERGE 90------------------ 91 92Often the current branch head is an ancestor of the named commit. 93This is the most common case especially when invoked from 'git 94pull': you are tracking an upstream repository, you have committed 95no local changes, and now you want to update to a newer upstream 96revision. In this case, a new commit is not needed to store the 97combined history; instead, the `HEAD` (along with the index) is 98updated to point at the named commit, without creating an extra 99merge commit. 100 101This behavior can be suppressed with the `--no-ff` option. 102 103HOW MERGE WORKS 104--------------- 105 106A merge is always between the current `HEAD` and one or more 107commits (usually a branch head or tag). 108 109Except in a fast-forward merge (see above), the branches to be 110merged must be tied together by a merge commit that has both of them 111as its parents. 112The rest of this section describes this "True merge" case. 113 114The chosen merge strategy merges the two commits into a single 115new source tree. 116When things merge cleanly, this is what happens: 117 1181. The results are updated both in the index file and in your 119 working tree; 1202. Index file is written out as a tree; 1213. The tree gets committed; and 1224. The `HEAD` pointer gets advanced. 123 124Because of 2., we require that the original state of the index 125file matches exactly the current `HEAD` commit; otherwise we 126will write out your local changes already registered in your 127index file along with the merge result, which is not good. 128Because 1. involves only those paths differing between your 129branch and the branch you are merging 130(which is typically a fraction of the whole tree), you can 131have local modifications in your working tree as long as they do 132not overlap with what the merge updates. 133 134When there are conflicts, the following happens: 135 1361. `HEAD` stays the same. 137 1382. Cleanly merged paths are updated both in the index file and 139 in your working tree. 140 1413. For conflicting paths, the index file records up to three 142 versions; stage1 stores the version from the common ancestor, 143 stage2 from `HEAD`, and stage3 from the other branch (you 144 can inspect the stages with `git ls-files -u`). The working 145 tree files contain the result of the "merge" program; i.e. 3-way 146 merge results with familiar conflict markers `<<< === >>>`. 147 1484. No other changes are done. In particular, the local 149 modifications you had before you started merge will stay the 150 same and the index entries for them stay as they were, 151 i.e. matching `HEAD`. 152 153If you tried a merge which resulted in complex conflicts and 154want to start over, you can recover with `git reset --merge`. 155 156HOW CONFLICTS ARE PRESENTED 157--------------------------- 158 159During a merge, the working tree files are updated to reflect the result 160of the merge. Among the changes made to the common ancestor's version, 161non-overlapping ones (that is, you changed an area of the file while the 162other side left that area intact, or vice versa) are incorporated in the 163final result verbatim. When both sides made changes to the same area, 164however, git cannot randomly pick one side over the other, and asks you to 165resolve it by leaving what both sides did to that area. 166 167By default, git uses the same style as that is used by "merge" program 168from the RCS suite to present such a conflicted hunk, like this: 169 170------------ 171Here are lines that are either unchanged from the common 172ancestor, or cleanly resolved because only one side changed. 173<<<<<<< yours:sample.txt 174Conflict resolution is hard; 175let's go shopping. 176======= 177Git makes conflict resolution easy. 178>>>>>>> theirs:sample.txt 179And here is another line that is cleanly resolved or unmodified. 180------------ 181 182The area where a pair of conflicting changes happened is marked with markers 183`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======` 184is typically your side, and the part afterwards is typically their side. 185 186The default format does not show what the original said in the conflicting 187area. You cannot tell how many lines are deleted and replaced with 188Barbie's remark on your side. The only thing you can tell is that your 189side wants to say it is hard and you'd prefer to go shopping, while the 190other side wants to claim it is easy. 191 192An alternative style can be used by setting the "merge.conflictstyle" 193configuration variable to "diff3". In "diff3" style, the above conflict 194may look like this: 195 196------------ 197Here are lines that are either unchanged from the common 198ancestor, or cleanly resolved because only one side changed. 199<<<<<<< yours:sample.txt 200Conflict resolution is hard; 201let's go shopping. 202||||||| 203Conflict resolution is hard. 204======= 205Git makes conflict resolution easy. 206>>>>>>> theirs:sample.txt 207And here is another line that is cleanly resolved or unmodified. 208------------ 209 210In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses 211another `|||||||` marker that is followed by the original text. You can 212tell that the original just stated a fact, and your side simply gave in to 213that statement and gave up, while the other side tried to have a more 214positive attitude. You can sometimes come up with a better resolution by 215viewing the original. 216 217 218HOW TO RESOLVE CONFLICTS 219------------------------ 220 221After seeing a conflict, you can do two things: 222 223 * Decide not to merge. The only clean-ups you need are to reset 224 the index file to the `HEAD` commit to reverse 2. and to clean 225 up working tree changes made by 2. and 3.; `git-reset --hard` can 226 be used for this. 227 228 * Resolve the conflicts. Git will mark the conflicts in 229 the working tree. Edit the files into shape and 230 'git add' them to the index. Use 'git commit' to seal the deal. 231 232You can work through the conflict with a number of tools: 233 234 * Use a mergetool. `git mergetool` to launch a graphical 235 mergetool which will work you through the merge. 236 237 * Look at the diffs. `git diff` will show a three-way diff, 238 highlighting changes from both the HEAD and their versions. 239 240 * Look at the diffs on their own. `git log --merge -p <path>` 241 will show diffs first for the HEAD version and then 242 their version. 243 244 * Look at the originals. `git show :1:filename` shows the 245 common ancestor, `git show :2:filename` shows the HEAD 246 version and `git show :3:filename` shows their version. 247 248 249EXAMPLES 250-------- 251 252* Merge branches `fixes` and `enhancements` on top of 253 the current branch, making an octopus merge: 254+ 255------------------------------------------------ 256$ git merge fixes enhancements 257------------------------------------------------ 258 259* Merge branch `obsolete` into the current branch, using `ours` 260 merge strategy: 261+ 262------------------------------------------------ 263$ git merge -s ours obsolete 264------------------------------------------------ 265 266* Merge branch `maint` into the current branch, but do not make 267 a new commit automatically: 268+ 269------------------------------------------------ 270$ git merge --no-commit maint 271------------------------------------------------ 272+ 273This can be used when you want to include further changes to the 274merge, or want to write your own merge commit message. 275+ 276You should refrain from abusing this option to sneak substantial 277changes into a merge commit. Small fixups like bumping 278release/version name would be acceptable. 279 280 281include::merge-strategies.txt[] 282 283CONFIGURATION 284------------- 285include::merge-config.txt[] 286 287branch.<name>.mergeoptions:: 288 Sets default options for merging into branch <name>. The syntax and 289 supported options are the same as those of 'git merge', but option 290 values containing whitespace characters are currently not supported. 291 292SEE ALSO 293-------- 294linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], 295linkgit:gitattributes[5], 296linkgit:git-reset[1], 297linkgit:git-diff[1], linkgit:git-ls-files[1], 298linkgit:git-add[1], linkgit:git-rm[1], 299linkgit:git-mergetool[1] 300 301Author 302------ 303Written by Junio C Hamano <gitster@pobox.com> 304 305 306Documentation 307-------------- 308Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. 309 310GIT 311--- 312Part of the linkgit:git[1] suite