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----------- 18Merges the history specified by <commit> into HEAD, optionally using a 19specific merge strategy. 20 21The second syntax (<msg> `HEAD` <commit>...) 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> <commit>...`. 24 25*Warning*: Running 'git-merge' with uncommitted changes is 26discouraged: while possible, it leaves you in a state that is hard to 27back out of in the case of a conflict. 28 29 30OPTIONS 31------- 32include::merge-options.txt[] 33 34-m <msg>:: 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. 39 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. 44 45include::merge-strategies.txt[] 46 47 48If you tried a merge which resulted in complex conflicts and 49want to start over, you can recover with 'git-reset'. 50 51CONFIGURATION 52------------- 53include::merge-config.txt[] 54 55branch.<name>.mergeoptions:: 56 Sets default options for merging into branch <name>. The syntax and 57 supported options are the same as those of 'git merge', but option 58 values containing whitespace characters are currently not supported. 59 60HOW MERGE WORKS 61--------------- 62 63A merge is always between the current `HEAD` and one or more 64commits (usually, branch head or tag), and the index file must 65match the tree of `HEAD` commit (i.e. the contents of the last commit) 66when it starts out. In other words, `git diff --cached HEAD` must 67report no changes. (One exception is when the changed index 68entries are already in the same state that would result from 69the merge anyway.) 70 71Three kinds of merge can happen: 72 73* The merged commit is already contained in `HEAD`. This is the 74 simplest case, called "Already up-to-date." 75 76* `HEAD` is already contained in the merged commit. This is the 77 most common case especially when invoked from 'git pull': 78 you are tracking an upstream repository, have committed no local 79 changes and now you want to update to a newer upstream revision. 80 Your `HEAD` (and the index) is updated to point at the merged 81 commit, without creating an extra merge commit. This is 82 called "Fast-forward". 83 84* Both the merged commit and `HEAD` are independent and must be 85 tied together by a merge commit that has both of them as its parents. 86 The rest of this section describes this "True merge" case. 87 88The chosen merge strategy merges the two commits into a single 89new source tree. 90When things merge cleanly, this is what happens: 91 921. The results are updated both in the index file and in your 93 working tree; 942. Index file is written out as a tree; 953. The tree gets committed; and 964. The `HEAD` pointer gets advanced. 97 98Because of 2., we require that the original state of the index 99file matches exactly the current `HEAD` commit; otherwise we 100will write out your local changes already registered in your 101index file along with the merge result, which is not good. 102Because 1. involves only those paths differing between your 103branch and the branch you are merging 104(which is typically a fraction of the whole tree), you can 105have local modifications in your working tree as long as they do 106not overlap with what the merge updates. 107 108When there are conflicts, the following happens: 109 1101. `HEAD` stays the same. 111 1122. Cleanly merged paths are updated both in the index file and 113 in your working tree. 114 1153. For conflicting paths, the index file records up to three 116 versions; stage1 stores the version from the common ancestor, 117 stage2 from `HEAD`, and stage3 from the other branch (you 118 can inspect the stages with `git ls-files -u`). The working 119 tree files contain the result of the "merge" program; i.e. 3-way 120 merge results with familiar conflict markers `<<< === >>>`. 121 1224. No other changes are done. In particular, the local 123 modifications you had before you started merge will stay the 124 same and the index entries for them stay as they were, 125 i.e. matching `HEAD`. 126 127HOW CONFLICTS ARE PRESENTED 128--------------------------- 129 130During a merge, the working tree files are updated to reflect the result 131of the merge. Among the changes made to the common ancestor's version, 132non-overlapping ones (that is, you changed an area of the file while the 133other side left that area intact, or vice versa) are incorporated in the 134final result verbatim. When both sides made changes to the same area, 135however, git cannot randomly pick one side over the other, and asks you to 136resolve it by leaving what both sides did to that area. 137 138By default, git uses the same style as that is used by "merge" program 139from the RCS suite to present such a conflicted hunk, like this: 140 141------------ 142Here are lines that are either unchanged from the common 143ancestor, or cleanly resolved because only one side changed. 144<<<<<<< yours:sample.txt 145Conflict resolution is hard; 146let's go shopping. 147======= 148Git makes conflict resolution easy. 149>>>>>>> theirs:sample.txt 150And here is another line that is cleanly resolved or unmodified. 151------------ 152 153The area where a pair of conflicting changes happened is marked with markers 154`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======` 155is typically your side, and the part afterwards is typically their side. 156 157The default format does not show what the original said in the conflicting 158area. You cannot tell how many lines are deleted and replaced with 159Barbie's remark on your side. The only thing you can tell is that your 160side wants to say it is hard and you'd prefer to go shopping, while the 161other side wants to claim it is easy. 162 163An alternative style can be used by setting the "merge.conflictstyle" 164configuration variable to "diff3". In "diff3" style, the above conflict 165may look like this: 166 167------------ 168Here are lines that are either unchanged from the common 169ancestor, or cleanly resolved because only one side changed. 170<<<<<<< yours:sample.txt 171Conflict resolution is hard; 172let's go shopping. 173||||||| 174Conflict resolution is hard. 175======= 176Git makes conflict resolution easy. 177>>>>>>> theirs:sample.txt 178And here is another line that is cleanly resolved or unmodified. 179------------ 180 181In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses 182another `|||||||` marker that is followed by the original text. You can 183tell that the original just stated a fact, and your side simply gave in to 184that statement and gave up, while the other side tried to have a more 185positive attitude. You can sometimes come up with a better resolution by 186viewing the original. 187 188 189HOW TO RESOLVE CONFLICTS 190------------------------ 191 192After seeing a conflict, you can do two things: 193 194 * Decide not to merge. The only clean-ups you need are to reset 195 the index file to the `HEAD` commit to reverse 2. and to clean 196 up working tree changes made by 2. and 3.; `git-reset --hard` can 197 be used for this. 198 199 * Resolve the conflicts. Git will mark the conflicts in 200 the working tree. Edit the files into shape and 201 'git-add' them to the index. Use 'git-commit' to seal the deal. 202 203You can work through the conflict with a number of tools: 204 205 * Use a mergetool. `git mergetool` to launch a graphical 206 mergetool which will work you through the merge. 207 208 * Look at the diffs. `git diff` will show a three-way diff, 209 highlighting changes from both the HEAD and their versions. 210 211 * Look at the diffs on their own. `git log --merge -p <path>` 212 will show diffs first for the HEAD version and then 213 their version. 214 215 * Look at the originals. `git show :1:filename` shows the 216 common ancestor, `git show :2:filename` shows the HEAD 217 version and `git show :3:filename` shows their version. 218 219 220EXAMPLES 221-------- 222 223* Merge branches `fixes` and `enhancements` on top of 224 the current branch, making an octopus merge: 225+ 226------------------------------------------------ 227$ git merge fixes enhancements 228------------------------------------------------ 229 230* Merge branch `obsolete` into the current branch, using `ours` 231 merge strategy: 232+ 233------------------------------------------------ 234$ git merge -s ours obsolete 235------------------------------------------------ 236 237* Merge branch `maint` into the current branch, but do not make 238 a new commit automatically: 239+ 240------------------------------------------------ 241$ git merge --no-commit maint 242------------------------------------------------ 243+ 244This can be used when you want to include further changes to the 245merge, or want to write your own merge commit message. 246+ 247You should refrain from abusing this option to sneak substantial 248changes into a merge commit. Small fixups like bumping 249release/version name would be acceptable. 250 251 252SEE ALSO 253-------- 254linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], 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] 260 261Author 262------ 263Written by Junio C Hamano <gitster@pobox.com> 264 265 266Documentation 267-------------- 268Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. 269 270GIT 271--- 272Part of the linkgit:git[1] suite