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SYNOPSIS
--------
[verse]
-'git merge' [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]...
- [-m <msg>] <remote> <remote>...
-'git merge' <msg> HEAD <remote>...
+'git merge' [-n] [--stat] [--no-commit] [--squash]
+ [-s <strategy>] [-X <strategy-option>]
+ [--[no-]rerere-autoupdate] [-m <msg>] [<commit>...]
+'git merge' <msg> HEAD <commit>...
+'git merge' --abort
DESCRIPTION
-----------
-This is the top-level interface to the merge machinery
-which drives multiple merge strategy scripts.
-
-The second syntax (<msg> `HEAD` <remote>) is supported for
+Incorporates changes from the named commits (since the time their
+histories diverged from the current branch) into the current
+branch. This command is used by 'git pull' to incorporate changes
+from another repository and can be used by hand to merge changes
+from one branch into another.
+
+Assume the following history exists and the current branch is
+"`master`":
+
+------------
+ A---B---C topic
+ /
+ D---E---F---G master
+------------
+
+Then "`git merge topic`" will replay the changes made on the
+`topic` branch since it diverged from `master` (i.e., `E`) until
+its current commit (`C`) on top of `master`, and record the result
+in a new commit along with the names of the two parent commits and
+a log message from the user describing the changes.
+
+------------
+ A---B---C topic
+ / \
+ D---E---F---G---H master
+------------
+
+The second syntax (<msg> `HEAD` <commit>...) is supported for
historical reasons. Do not use it from the command line or in
-new scripts. It is the same as `git merge -m <msg> <remote>`.
+new scripts. It is the same as `git merge -m <msg> <commit>...`.
+
+The third syntax ("`git merge --abort`") can only be run after the
+merge has resulted in conflicts. 'git merge --abort' will abort the
+merge process and try to reconstruct the pre-merge state. However,
+if there were uncommitted changes when the merge started (and
+especially if those changes were further modified after the merge
+was started), 'git merge --abort' will in some cases be unable to
+reconstruct the original (pre-merge) changes. Therefore:
+
+*Warning*: Running 'git merge' with uncommitted changes is
+discouraged: while possible, it leaves you in a state that is hard to
+back out of in the case of a conflict.
OPTIONS
include::merge-options.txt[]
-m <msg>::
- The commit message to be used for the merge commit (in case
- it is created). The 'git-fmt-merge-msg' script can be used
- to give a good default for automated 'git-merge' invocations.
+ Set the commit message to be used for the merge commit (in
+ case one is created).
++
+If `--log` is specified, a shortlog of the commits being merged
+will be appended to the specified message.
++
+The 'git fmt-merge-msg' command can be
+used to give a good default for automated 'git merge'
+invocations.
+
+--rerere-autoupdate::
+--no-rerere-autoupdate::
+ Allow the rerere mechanism to update the index with the
+ result of auto-conflict resolution if possible.
+
+--abort::
+ Abort the current conflict resolution process, and
+ try to reconstruct the pre-merge state.
++
+If there were uncommitted worktree changes present when the merge
+started, 'git merge --abort' will in some cases be unable to
+reconstruct these changes. It is therefore recommended to always
+commit or stash your changes before running 'git merge'.
++
+'git merge --abort' is equivalent to 'git reset --merge' when
+`MERGE_HEAD` is present.
+
+<commit>...::
+ Commits, usually other branch heads, to merge into our branch.
+ Specifying more than one commit will create a merge with
+ more than two parents (affectionately called an Octopus merge).
++
+If no commit is given from the command line, and if `merge.defaultToUpstream`
+configuration variable is set, merge the remote tracking branches
+that the current branch is configured to use as its upstream.
+See also the configuration section of this manual page.
+
+
+PRE-MERGE CHECKS
+----------------
+
+Before applying outside changes, you should get your own work in
+good shape and committed locally, so it will not be clobbered if
+there are conflicts. See also linkgit:git-stash[1].
+'git pull' and 'git merge' will stop without doing anything when
+local uncommitted changes overlap with files that 'git pull'/'git
+merge' may need to update.
+
+To avoid recording unrelated changes in the merge commit,
+'git pull' and 'git merge' will also abort if there are any changes
+registered in the index relative to the `HEAD` commit. (One
+exception is when the changed index entries are in the state that
+would result from the merge already.)
+
+If all named commits are already ancestors of `HEAD`, 'git merge'
+will exit early with the message "Already up-to-date."
+
+FAST-FORWARD MERGE
+------------------
+
+Often the current branch head is an ancestor of the named commit.
+This is the most common case especially when invoked from 'git
+pull': you are tracking an upstream repository, you have committed
+no local changes, and now you want to update to a newer upstream
+revision. In this case, a new commit is not needed to store the
+combined history; instead, the `HEAD` (along with the index) is
+updated to point at the named commit, without creating an extra
+merge commit.
+
+This behavior can be suppressed with the `--no-ff` option.
+
+TRUE MERGE
+----------
+
+Except in a fast-forward merge (see above), the branches to be
+merged must be tied together by a merge commit that has both of them
+as its parents.
+
+A merged version reconciling the changes from all branches to be
+merged is committed, and your `HEAD`, index, and working tree are
+updated to it. It is possible to have modifications in the working
+tree as long as they do not overlap; the update will preserve them.
+
+When it is not obvious how to reconcile the changes, the following
+happens:
+
+1. The `HEAD` pointer stays the same.
+2. The `MERGE_HEAD` ref is set to point to the other branch head.
+3. Paths that merged cleanly are updated both in the index file and
+ in your working tree.
+4. For conflicting paths, the index file records up to three
+ versions: stage 1 stores the version from the common ancestor,
+ stage 2 from `HEAD`, and stage 3 from `MERGE_HEAD` (you
+ can inspect the stages with `git ls-files -u`). The working
+ tree files contain the result of the "merge" program; i.e. 3-way
+ merge results with familiar conflict markers `<<<` `===` `>>>`.
+5. No other changes are made. In particular, the local
+ modifications you had before you started merge will stay the
+ same and the index entries for them stay as they were,
+ i.e. matching `HEAD`.
-<remote>...::
- Other branch heads to merge into our branch. You need at
- least one <remote>. Specifying more than one <remote>
- obviously means you are trying an Octopus.
+If you tried a merge which resulted in complex conflicts and
+want to start over, you can recover with `git merge --abort`.
+
+HOW CONFLICTS ARE PRESENTED
+---------------------------
+
+During a merge, the working tree files are updated to reflect the result
+of the merge. Among the changes made to the common ancestor's version,
+non-overlapping ones (that is, you changed an area of the file while the
+other side left that area intact, or vice versa) are incorporated in the
+final result verbatim. When both sides made changes to the same area,
+however, git cannot randomly pick one side over the other, and asks you to
+resolve it by leaving what both sides did to that area.
+
+By default, git uses the same style as that is used by "merge" program
+from the RCS suite to present such a conflicted hunk, like this:
+
+------------
+Here are lines that are either unchanged from the common
+ancestor, or cleanly resolved because only one side changed.
+<<<<<<< yours:sample.txt
+Conflict resolution is hard;
+let's go shopping.
+=======
+Git makes conflict resolution easy.
+>>>>>>> theirs:sample.txt
+And here is another line that is cleanly resolved or unmodified.
+------------
+
+The area where a pair of conflicting changes happened is marked with markers
+`<<<<<<<`, `=======`, and `>>>>>>>`. The part before the `=======`
+is typically your side, and the part afterwards is typically their side.
+
+The default format does not show what the original said in the conflicting
+area. You cannot tell how many lines are deleted and replaced with
+Barbie's remark on your side. The only thing you can tell is that your
+side wants to say it is hard and you'd prefer to go shopping, while the
+other side wants to claim it is easy.
+
+An alternative style can be used by setting the "merge.conflictstyle"
+configuration variable to "diff3". In "diff3" style, the above conflict
+may look like this:
+
+------------
+Here are lines that are either unchanged from the common
+ancestor, or cleanly resolved because only one side changed.
+<<<<<<< yours:sample.txt
+Conflict resolution is hard;
+let's go shopping.
+|||||||
+Conflict resolution is hard.
+=======
+Git makes conflict resolution easy.
+>>>>>>> theirs:sample.txt
+And here is another line that is cleanly resolved or unmodified.
+------------
+
+In addition to the `<<<<<<<`, `=======`, and `>>>>>>>` markers, it uses
+another `|||||||` marker that is followed by the original text. You can
+tell that the original just stated a fact, and your side simply gave in to
+that statement and gave up, while the other side tried to have a more
+positive attitude. You can sometimes come up with a better resolution by
+viewing the original.
+
+
+HOW TO RESOLVE CONFLICTS
+------------------------
-include::merge-strategies.txt[]
+After seeing a conflict, you can do two things:
+ * Decide not to merge. The only clean-ups you need are to reset
+ the index file to the `HEAD` commit to reverse 2. and to clean
+ up working tree changes made by 2. and 3.; `git merge --abort`
+ can be used for this.
-If you tried a merge which resulted in a complex conflicts and
-would want to start over, you can recover with 'git-reset'.
+ * Resolve the conflicts. Git will mark the conflicts in
+ the working tree. Edit the files into shape and
+ 'git add' them to the index. Use 'git commit' to seal the deal.
-CONFIGURATION
--------------
-include::merge-config.txt[]
+You can work through the conflict with a number of tools:
-branch.<name>.mergeoptions::
- Sets default options for merging into branch <name>. The syntax and
- supported options are equal to that of 'git-merge', but option values
- containing whitespace characters are currently not supported.
-
-HOW MERGE WORKS
----------------
-
-A merge is always between the current `HEAD` and one or more
-commits (usually, branch head or tag), and the index file must
-match the tree of `HEAD` commit (i.e. the contents of the last commit)
-when it starts out. In other words, `git diff --cached HEAD` must
-report no changes. (One exception is when the changed index
-entries are already in the same state that would result from
-the merge anyway.)
-
-Three kinds of merge can happen:
-
-* The merged commit is already contained in `HEAD`. This is the
- simplest case, called "Already up-to-date."
-
-* `HEAD` is already contained in the merged commit. This is the
- most common case especially when involved through 'git pull':
- you are tracking an upstream repository, committed no local
- changes and now you want to update to a newer upstream revision.
- Your `HEAD` (and the index) is updated to at point the merged
- commit, without creating an extra merge commit. This is
- called "Fast-forward".
-
-* Both the merged commit and `HEAD` are independent and must be
- tied together by a merge commit that has them both as its parents.
- The rest of this section describes this "True merge" case.
-
-The chosen merge strategy merges the two commits into a single
-new source tree.
-When things cleanly merge, these things happen:
-
-1. The results are updated both in the index file and in your
- working tree;
-2. Index file is written out as a tree;
-3. The tree gets committed; and
-4. The `HEAD` pointer gets advanced.
-
-Because of 2., we require that the original state of the index
-file to match exactly the current `HEAD` commit; otherwise we
-will write out your local changes already registered in your
-index file along with the merge result, which is not good.
-Because 1. involves only the paths different between your
-branch and the remote branch you are pulling from during the
-merge (which is typically a fraction of the whole tree), you can
-have local modifications in your working tree as long as they do
-not overlap with what the merge updates.
-
-When there are conflicts, these things happen:
-
-1. `HEAD` stays the same.
-
-2. Cleanly merged paths are updated both in the index file and
- in your working tree.
+ * Use a mergetool. `git mergetool` to launch a graphical
+ mergetool which will work you through the merge.
-3. For conflicting paths, the index file records up to three
- versions; stage1 stores the version from the common ancestor,
- stage2 from `HEAD`, and stage3 from the remote branch (you
- can inspect the stages with `git ls-files -u`). The working
- tree files have the result of "merge" program; i.e. 3-way
- merge result with familiar conflict markers `<<< === >>>`.
+ * Look at the diffs. `git diff` will show a three-way diff,
+ highlighting changes from both the `HEAD` and `MERGE_HEAD`
+ versions.
-4. No other changes are done. In particular, the local
- modifications you had before you started merge will stay the
- same and the index entries for them stay as they were,
- i.e. matching `HEAD`.
+ * Look at the diffs from each branch. `git log --merge -p <path>`
+ will show diffs first for the `HEAD` version and then the
+ `MERGE_HEAD` version.
-After seeing a conflict, you can do two things:
+ * Look at the originals. `git show :1:filename` shows the
+ common ancestor, `git show :2:filename` shows the `HEAD`
+ version, and `git show :3:filename` shows the `MERGE_HEAD`
+ version.
- * Decide not to merge. The only clean-up you need are to reset
- the index file to the `HEAD` commit to reverse 2. and to clean
- up working tree changes made by 2. and 3.; 'git-reset --hard' can
- be used for this.
- * Resolve the conflicts. `git diff` would report only the
- conflicting paths because of the above 2. and 3.
- Edit the working tree files into a desirable shape
- ('git mergetool' can ease this task), 'git-add' or 'git-rm'
- them, to make the index file contain what the merge result
- should be, and run 'git-commit' to commit the result.
+EXAMPLES
+--------
+
+* Merge branches `fixes` and `enhancements` on top of
+ the current branch, making an octopus merge:
++
+------------------------------------------------
+$ git merge fixes enhancements
+------------------------------------------------
+
+* Merge branch `obsolete` into the current branch, using `ours`
+ merge strategy:
++
+------------------------------------------------
+$ git merge -s ours obsolete
+------------------------------------------------
+
+* Merge branch `maint` into the current branch, but do not make
+ a new commit automatically:
++
+------------------------------------------------
+$ git merge --no-commit maint
+------------------------------------------------
++
+This can be used when you want to include further changes to the
+merge, or want to write your own merge commit message.
++
+You should refrain from abusing this option to sneak substantial
+changes into a merge commit. Small fixups like bumping
+release/version name would be acceptable.
+
+
+include::merge-strategies.txt[]
+
+CONFIGURATION
+-------------
+include::merge-config.txt[]
+branch.<name>.mergeoptions::
+ Sets default options for merging into branch <name>. The syntax and
+ supported options are the same as those of 'git merge', but option
+ values containing whitespace characters are currently not supported.
SEE ALSO
--------
linkgit:git-add[1], linkgit:git-rm[1],
linkgit:git-mergetool[1]
-Author
-------
-Written by Junio C Hamano <gitster@pobox.com>
-
-
-Documentation
---------------
-Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
-
GIT
---
Part of the linkgit:git[1] suite