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* jc/better-conflict-resolution: Fix AsciiDoc errors in merge documentation git-merge documentation: describe how conflict is presented checkout --conflict=<style>: recreate merge in a non-default style checkout -m: recreate merge when checking out of unmerged index git-merge-recursive: learn to honor merge.conflictstyle merge.conflictstyle: choose between "merge" and "diff3 -m" styles rerere: understand "diff3 -m" style conflicts with the original rerere.c: use symbolic constants to keep track of parsing states xmerge.c: "diff3 -m" style clips merge reduction level to EAGER or less xmerge.c: minimum readability fixups xdiff-merge: optionally show conflicts in "diff3 -m" style xdl_fill_merge_buffer(): separate out a too deeply nested function checkout --ours/--theirs: allow checking out one side of a conflicting merge checkout -f: allow ignoring unmerged paths when checking out of the index Conflicts: Documentation/git-checkout.txt builtin-checkout.c builtin-merge-recursive.c t/t7201-co.sh
234 lines
8.1 KiB
Text
234 lines
8.1 KiB
Text
git-merge(1)
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============
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NAME
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----
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git-merge - Join two or more development histories together
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SYNOPSIS
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--------
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[verse]
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'git merge' [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]...
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[-m <msg>] <remote> <remote>...
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'git merge' <msg> HEAD <remote>...
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DESCRIPTION
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-----------
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This is the top-level interface to the merge machinery
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which drives multiple merge strategy scripts.
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The second syntax (<msg> `HEAD` <remote>) is supported for
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historical reasons. Do not use it from the command line or in
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new scripts. It is the same as `git merge -m <msg> <remote>`.
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OPTIONS
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-------
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include::merge-options.txt[]
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-m <msg>::
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The commit message to be used for the merge commit (in case
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it is created). The 'git-fmt-merge-msg' script can be used
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to give a good default for automated 'git-merge' invocations.
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<remote>...::
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Other branch heads to merge into our branch. You need at
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least one <remote>. Specifying more than one <remote>
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obviously means you are trying an Octopus.
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include::merge-strategies.txt[]
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If you tried a merge which resulted in a complex conflicts and
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would want to start over, you can recover with 'git-reset'.
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CONFIGURATION
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-------------
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include::merge-config.txt[]
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branch.<name>.mergeoptions::
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Sets default options for merging into branch <name>. The syntax and
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supported options are equal to that of 'git-merge', but option values
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containing whitespace characters are currently not supported.
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HOW MERGE WORKS
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---------------
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A merge is always between the current `HEAD` and one or more
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commits (usually, branch head or tag), and the index file must
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match the tree of `HEAD` commit (i.e. the contents of the last commit)
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when it starts out. In other words, `git diff --cached HEAD` must
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report no changes. (One exception is when the changed index
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entries are already in the same state that would result from
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the merge anyway.)
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Three kinds of merge can happen:
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* The merged commit is already contained in `HEAD`. This is the
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simplest case, called "Already up-to-date."
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* `HEAD` is already contained in the merged commit. This is the
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most common case especially when involved through 'git pull':
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you are tracking an upstream repository, committed no local
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changes and now you want to update to a newer upstream revision.
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Your `HEAD` (and the index) is updated to at point the merged
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commit, without creating an extra merge commit. This is
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called "Fast-forward".
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* Both the merged commit and `HEAD` are independent and must be
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tied together by a merge commit that has them both as its parents.
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The rest of this section describes this "True merge" case.
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The chosen merge strategy merges the two commits into a single
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new source tree.
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When things cleanly merge, these things happen:
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1. The results are updated both in the index file and in your
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working tree;
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2. Index file is written out as a tree;
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3. The tree gets committed; and
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4. The `HEAD` pointer gets advanced.
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Because of 2., we require that the original state of the index
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file to match exactly the current `HEAD` commit; otherwise we
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will write out your local changes already registered in your
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index file along with the merge result, which is not good.
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Because 1. involves only the paths different between your
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branch and the remote branch you are pulling from during the
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merge (which is typically a fraction of the whole tree), you can
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have local modifications in your working tree as long as they do
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not overlap with what the merge updates.
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When there are conflicts, these things happen:
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1. `HEAD` stays the same.
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2. Cleanly merged paths are updated both in the index file and
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in your working tree.
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3. For conflicting paths, the index file records up to three
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versions; stage1 stores the version from the common ancestor,
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stage2 from `HEAD`, and stage3 from the remote branch (you
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can inspect the stages with `git ls-files -u`). The working
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tree files have the result of "merge" program; i.e. 3-way
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merge result with familiar conflict markers `<<< === >>>`.
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4. No other changes are done. In particular, the local
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modifications you had before you started merge will stay the
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same and the index entries for them stay as they were,
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i.e. matching `HEAD`.
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HOW CONFLICTS ARE PRESENTED
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---------------------------
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During a merge, the working tree files are updated to reflect the result
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of the merge. Among the changes made to the common ancestor's version,
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non-overlapping ones (that is, you changed an area of the file while the
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other side left that area intact, or vice versa) are incorporated in the
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final result verbatim. When both sides made changes to the same area,
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however, git cannot randomly pick one side over the other, and asks you to
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resolve it by leaving what both sides did to that area.
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By default, git uses the same style as that is used by "merge" program
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from the RCS suite to present such a conflicted hunk, like this:
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------------
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Here are lines that are either unchanged from the common
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ancestor, or cleanly resolved because only one side changed.
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<<<<<<< yours:sample.txt
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Conflict resolution is hard;
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let's go shopping.
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=======
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Git makes conflict resolution easy.
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>>>>>>> theirs:sample.txt
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And here is another line that is cleanly resolved or unmodified.
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------------
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The area a pair of conflicting changes happened is marked with markers
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"`<<<<<<<`", "`=======`", and "`>>>>>>>`". The part before the "`=======`"
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is typically your side, and the part after it is typically their side.
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The default format does not show what the original said in the conflicted
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area. You cannot tell how many lines are deleted and replaced with the
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Barbie's remark by your side. The only thing you can tell is that your
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side wants to say it is hard and you'd prefer to go shopping, while the
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other side wants to claim it is easy.
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An alternative style can be used by setting the "merge.conflictstyle"
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configuration variable to "diff3". In "diff3" style, the above conflict
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may look like this:
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------------
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Here are lines that are either unchanged from the common
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ancestor, or cleanly resolved because only one side changed.
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<<<<<<< yours:sample.txt
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Conflict resolution is hard;
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let's go shopping.
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|||||||
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Conflict resolution is hard.
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=======
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Git makes conflict resolution easy.
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>>>>>>> theirs:sample.txt
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And here is another line that is cleanly resolved or unmodified.
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------------
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In addition to the "`<<<<<<<`", "`=======`", and "`>>>>>>>`" markers, it uses
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another "`|||||||`" marker that is followed by the original text. You can
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tell that the original just stated a fact, and your side simply gave in to
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that statement and gave up, while the other side tried to have a more
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positive attitude. You can sometimes come up with a better resolution by
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viewing the original.
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HOW TO RESOLVE CONFLICTS
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------------------------
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After seeing a conflict, you can do two things:
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* Decide not to merge. The only clean-up you need are to reset
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the index file to the `HEAD` commit to reverse 2. and to clean
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up working tree changes made by 2. and 3.; 'git-reset --hard' can
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be used for this.
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* Resolve the conflicts. Git will mark the conflicts in
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the working tree. Edit the files into shape and
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'git-add' to the index. 'git-commit' to seal the deal.
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You can work through the conflict with a number of tools:
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* Use a mergetool. 'git mergetool' to launch a graphical
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mergetool which will work you through the merge.
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* Look at the diffs. 'git diff' will show a three-way diff,
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highlighting changes from both the HEAD and remote versions.
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* Look at the diffs on their own. 'git log --merge -p <path>'
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will show diffs first for the HEAD version and then the
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remote version.
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* Look at the originals. 'git show :1:filename' shows the
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common ancestor, 'git show :2:filename' shows the HEAD
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version and 'git show :3:filename' shows the remote version.
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SEE ALSO
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--------
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linkgit:git-fmt-merge-msg[1], linkgit:git-pull[1],
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linkgit:gitattributes[5],
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linkgit:git-reset[1],
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linkgit:git-diff[1], linkgit:git-ls-files[1],
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linkgit:git-add[1], linkgit:git-rm[1],
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linkgit:git-mergetool[1]
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Author
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------
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Written by Junio C Hamano <gitster@pobox.com>
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Documentation
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--------------
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Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
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GIT
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---
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Part of the linkgit:git[1] suite
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