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 [--[no-]rerere-autoupdate] [-m <msg>] <remote>... 14'git merge' <msg> HEAD <remote>... 15 16DESCRIPTION 17----------- 18This is the top-level interface to the merge machinery 19which drives multiple merge strategy scripts. 20 21The second syntax (<msg> `HEAD` <remote>) is supported for 22historical reasons. Do not use it from the command line or in 23new scripts. It is the same as `git merge -m <msg> <remote>`. 24 25 26OPTIONS 27------- 28include::merge-options.txt[] 29 30-m <msg>:: 31 Set the commit message to be used for the merge commit (in 32 case one is created). The 'git fmt-merge-msg' command can be 33 used to give a good default for automated 'git merge' 34 invocations. 35 36--rerere-autoupdate:: 37--no-rerere-autoupdate:: 38 Allow the rerere mechanism to update the index with the 39 result of auto-conflict resolution if possible. 40 41<remote>...:: 42 Other branch heads to merge into our branch. You need at 43 least one <remote>. Specifying more than one <remote> 44 obviously means you are trying an Octopus. 45 46include::merge-strategies.txt[] 47 48 49If you tried a merge which resulted in complex conflicts and 50want to start over, you can recover with 'git-reset'. 51 52CONFIGURATION 53------------- 54include::merge-config.txt[] 55 56branch.<name>.mergeoptions:: 57 Sets default options for merging into branch <name>. The syntax and 58 supported options are the same as those of 'git merge', but option 59 values containing whitespace characters are currently not supported. 60 61HOW MERGE WORKS 62--------------- 63 64A merge is always between the current `HEAD` and one or more 65commits (usually, branch head or tag), and the index file must 66match the tree of `HEAD` commit (i.e. the contents of the last commit) 67when it starts out. In other words, `git diff --cached HEAD` must 68report no changes. (One exception is when the changed index 69entries are already in the same state that would result from 70the merge anyway.) 71 72Three kinds of merge can happen: 73 74* The merged commit is already contained in `HEAD`. This is the 75 simplest case, called "Already up-to-date." 76 77* `HEAD` is already contained in the merged commit. This is the 78 most common case especially when invoked from 'git pull': 79 you are tracking an upstream repository, have committed no local 80 changes and now you want to update to a newer upstream revision. 81 Your `HEAD` (and the index) is updated to point at the merged 82 commit, without creating an extra merge commit. This is 83 called "Fast-forward". 84 85* Both the merged commit and `HEAD` are independent and must be 86 tied together by a merge commit that has both of them as its parents. 87 The rest of this section describes this "True merge" case. 88 89The chosen merge strategy merges the two commits into a single 90new source tree. 91When things merge cleanly, this is what happens: 92 931. The results are updated both in the index file and in your 94 working tree; 952. Index file is written out as a tree; 963. The tree gets committed; and 974. The `HEAD` pointer gets advanced. 98 99Because of 2., we require that the original state of the index 100file matches exactly the current `HEAD` commit; otherwise we 101will write out your local changes already registered in your 102index file along with the merge result, which is not good. 103Because 1. involves only those paths differing between your 104branch and the remote branch you are pulling from during the 105merge (which is typically a fraction of the whole tree), you can 106have local modifications in your working tree as long as they do 107not overlap with what the merge updates. 108 109When there are conflicts, the following happens: 110 1111. `HEAD` stays the same. 112 1132. Cleanly merged paths are updated both in the index file and 114 in your working tree. 115 1163. For conflicting paths, the index file records up to three 117 versions; stage1 stores the version from the common ancestor, 118 stage2 from `HEAD`, and stage3 from the remote branch (you 119 can inspect the stages with `git ls-files -u`). The working 120 tree files contain the result of the "merge" program; i.e. 3-way 121 merge results with familiar conflict markers `<<< === >>>`. 122 1234. No other changes are done. In particular, the local 124 modifications you had before you started merge will stay the 125 same and the index entries for them stay as they were, 126 i.e. matching `HEAD`. 127 128HOW CONFLICTS ARE PRESENTED 129--------------------------- 130 131During a merge, the working tree files are updated to reflect the result 132of the merge. Among the changes made to the common ancestor's version, 133non-overlapping ones (that is, you changed an area of the file while the 134other side left that area intact, or vice versa) are incorporated in the 135final result verbatim. When both sides made changes to the same area, 136however, git cannot randomly pick one side over the other, and asks you to 137resolve it by leaving what both sides did to that area. 138 139By default, git uses the same style as that is used by "merge" program 140from the RCS suite to present such a conflicted hunk, like this: 141 142------------ 143Here are lines that are either unchanged from the common 144ancestor, or cleanly resolved because only one side changed. 145<<<<<<< yours:sample.txt 146Conflict resolution is hard; 147let's go shopping. 148======= 149Git makes conflict resolution easy. 150>>>>>>> theirs:sample.txt 151And here is another line that is cleanly resolved or unmodified. 152------------ 153 154The area where a pair of conflicting changes happened is marked with markers 155`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======` 156is typically your side, and the part afterwards is typically their side. 157 158The default format does not show what the original said in the conflicting 159area. You cannot tell how many lines are deleted and replaced with 160Barbie's remark on your side. The only thing you can tell is that your 161side wants to say it is hard and you'd prefer to go shopping, while the 162other side wants to claim it is easy. 163 164An alternative style can be used by setting the "merge.conflictstyle" 165configuration variable to "diff3". In "diff3" style, the above conflict 166may look like this: 167 168------------ 169Here are lines that are either unchanged from the common 170ancestor, or cleanly resolved because only one side changed. 171<<<<<<< yours:sample.txt 172Conflict resolution is hard; 173let's go shopping. 174||||||| 175Conflict resolution is hard. 176======= 177Git makes conflict resolution easy. 178>>>>>>> theirs:sample.txt 179And here is another line that is cleanly resolved or unmodified. 180------------ 181 182In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses 183another `|||||||` marker that is followed by the original text. You can 184tell that the original just stated a fact, and your side simply gave in to 185that statement and gave up, while the other side tried to have a more 186positive attitude. You can sometimes come up with a better resolution by 187viewing the original. 188 189 190HOW TO RESOLVE CONFLICTS 191------------------------ 192 193After seeing a conflict, you can do two things: 194 195 * Decide not to merge. The only clean-ups you need are to reset 196 the index file to the `HEAD` commit to reverse 2. and to clean 197 up working tree changes made by 2. and 3.; 'git-reset --hard' can 198 be used for this. 199 200 * Resolve the conflicts. Git will mark the conflicts in 201 the working tree. Edit the files into shape and 202 'git-add' them to the index. Use 'git-commit' to seal the deal. 203 204You can work through the conflict with a number of tools: 205 206 * Use a mergetool. 'git mergetool' to launch a graphical 207 mergetool which will work you through the merge. 208 209 * Look at the diffs. 'git diff' will show a three-way diff, 210 highlighting changes from both the HEAD and remote versions. 211 212 * Look at the diffs on their own. 'git log --merge -p <path>' 213 will show diffs first for the HEAD version and then the 214 remote version. 215 216 * Look at the originals. 'git show :1:filename' shows the 217 common ancestor, 'git show :2:filename' shows the HEAD 218 version and 'git show :3:filename' shows the remote version. 219 220 221EXAMPLES 222-------- 223 224* Merge branches `fixes` and `enhancements` on top of 225 the current branch, making an octopus merge: 226+ 227------------------------------------------------ 228$ git merge fixes enhancements 229------------------------------------------------ 230 231* Merge branch `obsolete` into the current branch, using `ours` 232 merge strategy: 233+ 234------------------------------------------------ 235$ git merge -s ours obsolete 236------------------------------------------------ 237 238* Merge branch `maint` into the current branch, but do not make 239 a new commit automatically: 240+ 241------------------------------------------------ 242$ git merge --no-commit maint 243------------------------------------------------ 244+ 245This can be used when you want to include further changes to the 246merge, or want to write your own merge commit message. 247+ 248You should refrain from abusing this option to sneak substantial 249changes into a merge commit. Small fixups like bumping 250release/version name would be acceptable. 251 252 253SEE ALSO 254-------- 255linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], 256linkgit:gitattributes[5], 257linkgit:git-reset[1], 258linkgit:git-diff[1], linkgit:git-ls-files[1], 259linkgit:git-add[1], linkgit:git-rm[1], 260linkgit:git-mergetool[1] 261 262Author 263------ 264Written by Junio C Hamano <gitster@pobox.com> 265 266 267Documentation 268-------------- 269Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. 270 271GIT 272--- 273Part of the linkgit:git[1] suite