Documentation/git-merge.txt - jrn/git - Git at Google

 git-merge(1)
 ============

 NAME
 ----
 git-merge - Join two or more development histories together


 SYNOPSIS
 --------
 [verse]
 'git merge' [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
 	[-s <strategy>] [-X <strategy-option>] [-S[<key-id>]]
 	[--[no-]rerere-autoupdate] [-m <msg>] [<commit>...]
 'git merge' <msg> HEAD <commit>...
 'git merge' --abort

 DESCRIPTION
 -----------
 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> <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 non-trivial uncommitted changes is
 discouraged: while possible, it may leave you in a state that is hard to
 back out of in the case of a conflict.


 OPTIONS
 -------
 include::merge-options.txt[]

 -S[<keyid>]::
 --gpg-sign[=<keyid>]::
 	GPG-sign the resulting merge commit.

 -m <msg>::
 	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.

 --[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`.

 If you tried a merge which resulted in complex conflicts and
 want to start over, you can recover with `git merge --abort`.

 MERGING TAG
 -----------

 When merging an annotated (and possibly signed) tag, Git always
 creates a merge commit even if a fast-forward merge is possible, and
 the commit message template is prepared with the tag message.
 Additionally, if the tag is signed, the signature check is reported
 as a comment in the message template. See also linkgit:git-tag[1].

 When you want to just integrate with the work leading to the commit
 that happens to be tagged, e.g. synchronizing with an upstream
 release point, you may not want to make an unnecessary merge commit.

 In such a case, you can "unwrap" the tag yourself before feeding it
 to `git merge`, or pass `--ff-only` when you do not have any work on
 your own. e.g.

 ----
 git fetch origin
 git merge v1.2.3^0
 git merge --ff-only v1.2.3
 ----


 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 the one used by the "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
 ------------------------

 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.

  * 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.

 You can work through the conflict with a number of tools:

  * Use a mergetool.  `git mergetool` to launch a graphical
    mergetool which will work you through the merge.

  * Look at the diffs.  `git diff` will show a three-way diff,
    highlighting changes from both the `HEAD` and `MERGE_HEAD`
    versions.

  * 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.

  * 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.


 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-fmt-merge-msg[1], linkgit:git-pull[1],
 linkgit:gitattributes[5],
 linkgit:git-reset[1],
 linkgit:git-diff[1], linkgit:git-ls-files[1],
 linkgit:git-add[1], linkgit:git-rm[1],
 linkgit:git-mergetool[1]

 GIT
 ---
 Part of the linkgit:git[1] suite
	git-merge(1)
	============

	NAME
	----
	git-merge - Join two or more development histories together


	SYNOPSIS
	--------
	[verse]
	'git merge' [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
	[-s <strategy>] [-X <strategy-option>] [-S[<key-id>]]
	[--[no-]rerere-autoupdate] [-m <msg>] [<commit>...]
	'git merge' <msg> HEAD <commit>...
	'git merge' --abort

	DESCRIPTION
	-----------
	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> <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 non-trivial uncommitted changes is
	discouraged: while possible, it may leave you in a state that is hard to
	back out of in the case of a conflict.


	OPTIONS
	-------
	include::merge-options.txt[]

	-S[<keyid>]::
	--gpg-sign[=<keyid>]::
	GPG-sign the resulting merge commit.

	-m <msg>::
	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.

	--[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`.

	If you tried a merge which resulted in complex conflicts and
	want to start over, you can recover with `git merge --abort`.

	MERGING TAG
	-----------

	When merging an annotated (and possibly signed) tag, Git always
	creates a merge commit even if a fast-forward merge is possible, and
	the commit message template is prepared with the tag message.
	Additionally, if the tag is signed, the signature check is reported
	as a comment in the message template. See also linkgit:git-tag[1].

	When you want to just integrate with the work leading to the commit
	that happens to be tagged, e.g. synchronizing with an upstream
	release point, you may not want to make an unnecessary merge commit.

	In such a case, you can "unwrap" the tag yourself before feeding it
	to `git merge`, or pass `--ff-only` when you do not have any work on
	your own. e.g.

	----
	git fetch origin
	git merge v1.2.3^0
	git merge --ff-only v1.2.3
	----


	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 the one used by the "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
	------------------------

	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.

	* 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.

	You can work through the conflict with a number of tools:

	* Use a mergetool. `git mergetool` to launch a graphical
	mergetool which will work you through the merge.

	* Look at the diffs. `git diff` will show a three-way diff,
	highlighting changes from both the `HEAD` and `MERGE_HEAD`
	versions.

	* 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.

	* 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.


	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-fmt-merge-msg[1], linkgit:git-pull[1],
	linkgit:gitattributes[5],
	linkgit:git-reset[1],
	linkgit:git-diff[1], linkgit:git-ls-files[1],
	linkgit:git-add[1], linkgit:git-rm[1],
	linkgit:git-mergetool[1]

	GIT
	---
	Part of the linkgit:git[1] suite