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>] <remote> <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 The commit message to be used for the merge commit (in case 32 it is created). The 'git-fmt-merge-msg' script can be used 33 to give a good default for automated 'git-merge' invocations. 34 35<remote>...:: 36 Other branch heads to merge into our branch. You need at 37 least one <remote>. Specifying more than one <remote> 38 obviously means you are trying an Octopus. 39 40include::merge-strategies.txt[] 41 42 43If you tried a merge which resulted in a complex conflicts and 44would want to start over, you can recover with 'git-reset'. 45 46CONFIGURATION 47------------- 48include::merge-config.txt[] 49 50branch.<name>.mergeoptions:: 51 Sets default options for merging into branch <name>. The syntax and 52 supported options are equal to that of 'git-merge', but option values 53 containing whitespace characters are currently not supported. 54 55HOW MERGE WORKS 56--------------- 57 58A merge is always between the current `HEAD` and one or more 59commits (usually, branch head or tag), and the index file must 60match the tree of `HEAD` commit (i.e. the contents of the last commit) 61when it starts out. In other words, `git diff --cached HEAD` must 62report no changes. (One exception is when the changed index 63entries are already in the same state that would result from 64the merge anyway.) 65 66Three kinds of merge can happen: 67 68* The merged commit is already contained in `HEAD`. This is the 69 simplest case, called "Already up-to-date." 70 71* `HEAD` is already contained in the merged commit. This is the 72 most common case especially when involved through 'git pull': 73 you are tracking an upstream repository, committed no local 74 changes and now you want to update to a newer upstream revision. 75 Your `HEAD` (and the index) is updated to at point the merged 76 commit, without creating an extra merge commit. This is 77 called "Fast-forward". 78 79* Both the merged commit and `HEAD` are independent and must be 80 tied together by a merge commit that has them both as its parents. 81 The rest of this section describes this "True merge" case. 82 83The chosen merge strategy merges the two commits into a single 84new source tree. 85When things cleanly merge, these things happen: 86 871. The results are updated both in the index file and in your 88 working tree; 892. Index file is written out as a tree; 903. The tree gets committed; and 914. The `HEAD` pointer gets advanced. 92 93Because of 2., we require that the original state of the index 94file to match exactly the current `HEAD` commit; otherwise we 95will write out your local changes already registered in your 96index file along with the merge result, which is not good. 97Because 1. involves only the paths different between your 98branch and the remote branch you are pulling from during the 99merge (which is typically a fraction of the whole tree), you can 100have local modifications in your working tree as long as they do 101not overlap with what the merge updates. 102 103When there are conflicts, these things happen: 104 1051. `HEAD` stays the same. 106 1072. Cleanly merged paths are updated both in the index file and 108 in your working tree. 109 1103. For conflicting paths, the index file records up to three 111 versions; stage1 stores the version from the common ancestor, 112 stage2 from `HEAD`, and stage3 from the remote branch (you 113 can inspect the stages with `git ls-files -u`). The working 114 tree files have the result of "merge" program; i.e. 3-way 115 merge result with familiar conflict markers `<<< === >>>`. 116 1174. No other changes are done. In particular, the local 118 modifications you had before you started merge will stay the 119 same and the index entries for them stay as they were, 120 i.e. matching `HEAD`. 121 122After seeing a conflict, you can do two things: 123 124 * Decide not to merge. The only clean-up you need are to reset 125 the index file to the `HEAD` commit to reverse 2. and to clean 126 up working tree changes made by 2. and 3.; 'git-reset --hard' can 127 be used for this. 128 129 * Resolve the conflicts. `git diff` would report only the 130 conflicting paths because of the above 2. and 3. 131 Edit the working tree files into a desirable shape 132 ('git mergetool' can ease this task), 'git-add' or 'git-rm' 133 them, to make the index file contain what the merge result 134 should be, and run 'git-commit' to commit the result. 135 136 137SEE ALSO 138-------- 139linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1], 140linkgit:gitattributes[5], 141linkgit:git-reset[1], 142linkgit:git-diff[1], linkgit:git-ls-files[1], 143linkgit:git-add[1], linkgit:git-rm[1], 144linkgit:git-mergetool[1] 145 146Author 147------ 148Written by Junio C Hamano <gitster@pobox.com> 149 150 151Documentation 152-------------- 153Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>. 154 155GIT 156--- 157Part of the linkgit:git[1] suite