NAME¶
git-merge - Join two or more development histories together
SYNOPSIS¶
git merge [-n] [--stat] [--no-commit] [--squash] [--[no-]edit]
[--no-verify] [-s <strategy>] [-X <strategy-option>] [-S[<keyid>]]
[--[no-]allow-unrelated-histories]
[--[no-]rerere-autoupdate] [-m <msg>] [-F <file>] [<commit>...]
git merge (--continue | --abort | --quit)
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 ("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.
The third syntax ("git merge --continue") can
only be run after the merge has resulted in conflicts.
OPTIONS¶
--commit, --no-commit
Perform the merge and commit the result. This option can
be used to override --no-commit.
With --no-commit perform the merge and stop just before creating a
merge commit, to give the user a chance to inspect and further tweak the
merge result before committing.
Note that fast-forward updates do not create a merge commit and
therefore there is no way to stop those merges with --no-commit. Thus, if
you want to ensure your branch is not changed or updated by the merge
command, use --no-ff with --no-commit.
--edit, -e, --no-edit
Invoke an editor before committing successful mechanical
merge to further edit the auto-generated merge message, so that the user can
explain and justify the merge. The
--no-edit option can be used to
accept the auto-generated message (this is generally discouraged). The
--edit (or
-e) option is still useful if you are giving a draft
message with the
-m option from the command line and want to edit it in
the editor.
Older scripts may depend on the historical behaviour of not
allowing the user to edit the merge log message. They will see an editor
opened when they run git merge. To make it easier to adjust such
scripts to the updated behaviour, the environment variable
GIT_MERGE_AUTOEDIT can be set to no at the beginning of
them.
--cleanup=<mode>
This option determines how the merge message will be
cleaned up before committing. See
git-commit(1) for more details. In
addition, if the
<mode> is given a value of
scissors,
scissors will be appended to
MERGE_MSG before being passed on to the
commit machinery in the case of a merge conflict.
--ff, --no-ff, --ff-only
Specifies how a merge is handled when the merged-in
history is already a descendant of the current history.
--ff is the
default unless merging an annotated (and possibly signed) tag that is not
stored in its natural place in the
refs/tags/ hierarchy, in which case
--no-ff is assumed.
With --ff, when possible resolve the merge as a
fast-forward (only update the branch pointer to match the merged branch; do
not create a merge commit). When not possible (when the merged-in history is
not a descendant of the current history), create a merge commit.
With --no-ff, create a merge commit in all cases, even when
the merge could instead be resolved as a fast-forward.
With --ff-only, resolve the merge as a fast-forward when
possible. When not possible, refuse to merge and exit with a non-zero
status.
-S[<keyid>], --gpg-sign[=<keyid>], --no-gpg-sign
GPG-sign the resulting merge commit. The keyid
argument is optional and defaults to the committer identity; if specified, it
must be stuck to the option without a space. --no-gpg-sign is useful to
countermand both commit.gpgSign configuration variable, and earlier
--gpg-sign.
--log[=<n>], --no-log
In addition to branch names, populate the log message
with one-line descriptions from at most <n> actual commits that are
being merged. See also
git-fmt-merge-msg(1).
With --no-log do not list one-line descriptions from the actual
commits being merged.
--signoff, --no-signoff
Add Signed-off-by line by the committer at the end of the
commit log message. The meaning of a signoff depends on the project, but it
typically certifies that committer has the rights to submit this work under
the same license and agrees to a Developer Certificate of Origin (see
http://developercertificate.org/ for more information).
With --no-signoff do not add a Signed-off-by line.
--stat, -n, --no-stat
Show a diffstat at the end of the merge. The diffstat is
also controlled by the configuration option merge.stat.
With -n or --no-stat do not show a diffstat at the end of the
merge.
--squash, --no-squash
Produce the working tree and index state as if a real
merge happened (except for the merge information), but do not actually make a
commit, move the
HEAD, or record
$GIT_DIR/MERGE_HEAD (to cause
the next
git commit command to create a merge commit). This allows you
to create a single commit on top of the current branch whose effect is the
same as merging another branch (or more in case of an octopus).
With --no-squash perform the merge and commit the result. This
option can be used to override --squash.
With --squash, --commit is not allowed, and will fail.
--no-verify
This option bypasses the pre-merge and commit-msg hooks.
See also
githooks(5).
-s <strategy>, --strategy=<strategy>
Use the given merge strategy; can be supplied more than
once to specify them in the order they should be tried. If there is no
-s option, a built-in list of strategies is used instead (git
merge-recursive when merging a single head, git merge-octopus
otherwise).
-X <option>, --strategy-option=<option>
Pass merge strategy specific option through to the merge
strategy.
--verify-signatures, --no-verify-signatures
Verify that the tip commit of the side branch being
merged is signed with a valid key, i.e. a key that has a valid uid: in the
default trust model, this means the signing key has been signed by a trusted
key. If the tip commit of the side branch is not signed with a valid key, the
merge is aborted.
--summary, --no-summary
Synonyms to --stat and --no-stat; these are deprecated
and will be removed in the future.
-q, --quiet
Operate quietly. Implies --no-progress.
-v, --verbose
Be verbose.
--progress, --no-progress
Turn progress on/off explicitly. If neither is specified,
progress is shown if standard error is connected to a terminal. Note that not
all merge strategies may support progress reporting.
--autostash, --no-autostash
Automatically create a temporary stash entry before the
operation begins, and apply it after the operation ends. This means that you
can run the operation on a dirty worktree. However, use with care: the final
stash application after a successful merge might result in non-trivial
conflicts.
--allow-unrelated-histories
By default, git merge command refuses to merge
histories that do not share a common ancestor. This option can be used to
override this safety when merging histories of two projects that started their
lives independently. As that is a very rare occasion, no configuration
variable to enable this by default exists and will not be added.
-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. The automated message
can include the branch description.
-F <file>, --file=<file>
Read 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.
--rerere-autoupdate, --no-rerere-autoupdate
Allow the rerere mechanism to update the index with the
result of auto-conflict resolution if possible.
--overwrite-ignore, --no-overwrite-ignore
Silently overwrite ignored files from the merge result.
This is the default behavior. Use --no-overwrite-ignore to abort.
--abort
Abort the current conflict resolution process, and try to
reconstruct the pre-merge state. If an autostash entry is present, apply it to
the worktree.
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 unless MERGE_AUTOSTASH is also
present in which case git merge --abort applies the stash entry to
the worktree whereas git reset --merge will save the stashed changes
in the stash list.
--quit
Forget about the current merge in progress. Leave the
index and the working tree as-is. If MERGE_AUTOSTASH is present, the
stash entry will be saved to the stash list.
--continue
After a git merge stops due to conflicts you can
conclude the merge by running git merge --continue (see "HOW TO
RESOLVE CONFLICTS" section below).
<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, 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.
When FETCH_HEAD (and no other commit) is specified, the
branches recorded in the .git/FETCH_HEAD file by the previous
invocation of git fetch for merging are merged to the current
branch.
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 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. (Special narrow
exceptions to this rule may exist depending on which merge strategy is in
use, but generally, the index must match HEAD.)
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
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 or git merge --continue to
seal the deal. The latter command checks whether there is a (interrupted)
merge in progress before calling git commit.
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.
MERGE STRATEGIES¶
The merge mechanism (git merge and git pull commands) allows the
backend merge strategies to be chosen with -s option. Some
strategies can also take their own options, which can be passed by giving
-X<option> arguments to git merge and/or git pull.
resolve
This can only resolve two heads (i.e. the current branch
and another branch you pulled from) using a 3-way merge algorithm. It tries to
carefully detect criss-cross merge ambiguities and is considered generally
safe and fast.
recursive
This can only resolve two heads using a 3-way merge
algorithm. When there is more than one common ancestor that can be used for
3-way merge, it creates a merged tree of the common ancestors and uses that as
the reference tree for the 3-way merge. This has been reported to result in
fewer merge conflicts without causing mismerges by tests done on actual merge
commits taken from Linux 2.6 kernel development history. Additionally this can
detect and handle merges involving renames, but currently cannot make use of
detected copies. This is the default merge strategy when pulling or merging
one branch.
The recursive strategy can take the following options:
ours
This option forces conflicting hunks to be auto-resolved
cleanly by favoring
our version. Changes from the other tree that do
not conflict with our side are reflected in the merge result. For a binary
file, the entire contents are taken from our side.
This should not be confused with the ours merge strategy,
which does not even look at what the other tree contains at all. It discards
everything the other tree did, declaring our history contains all
that happened in it.
theirs
This is the opposite of ours; note that, unlike
ours, there is no theirs merge strategy to confuse this merge
option with.
patience
With this option,
merge-recursive spends a little
extra time to avoid mismerges that sometimes occur due to unimportant matching
lines (e.g., braces from distinct functions). Use this when the branches to be
merged have diverged wildly. See also
git-diff(1)
--patience.
diff-algorithm=[patience|minimal|histogram|myers]
Tells
merge-recursive to use a different diff
algorithm, which can help avoid mismerges that occur due to unimportant
matching lines (such as braces from distinct functions). See also
git-diff(1) --diff-algorithm.
ignore-space-change, ignore-all-space, ignore-space-at-eol,
ignore-cr-at-eol
Treats lines with the indicated type of whitespace change
as unchanged for the sake of a three-way merge. Whitespace changes mixed with
other changes to a line are not ignored. See also
git-diff(1)
-b,
-w,
--ignore-space-at-eol, and
--ignore-cr-at-eol.
•If their version only introduces
whitespace changes to a line, our version is used;
•If our version introduces whitespace
changes but their version includes a substantial change, their
version is used;
•Otherwise, the merge proceeds in the usual
way.
renormalize
This runs a virtual check-out and check-in of all three
stages of a file when resolving a three-way merge. This option is meant to be
used when merging branches with different clean filters or end-of-line
normalization rules. See "Merging branches with differing
checkin/checkout attributes" in
gitattributes(5) for
details.
no-renormalize
Disables the renormalize option. This overrides
the merge.renormalize configuration variable.
no-renames
Turn off rename detection. This overrides the
merge.renames configuration variable. See also
git-diff(1)
--no-renames.
find-renames[=<n>]
Turn on rename detection, optionally setting the
similarity threshold. This is the default. This overrides the
merge.renames configuration variable. See also
git-diff(1)
--find-renames.
rename-threshold=<n>
Deprecated synonym for
find-renames=<n>.
subtree[=<path>]
This option is a more advanced form of subtree
strategy, where the strategy makes a guess on how two trees must be shifted to
match with each other when merging. Instead, the specified path is prefixed
(or stripped from the beginning) to make the shape of two trees to
match.
octopus
This resolves cases with more than two heads, but refuses
to do a complex merge that needs manual resolution. It is primarily meant to
be used for bundling topic branch heads together. This is the default merge
strategy when pulling or merging more than one branch.
ours
This resolves any number of heads, but the resulting tree
of the merge is always that of the current branch head, effectively ignoring
all changes from all other branches. It is meant to be used to supersede old
development history of side branches. Note that this is different from the
-Xours option to the recursive merge strategy.
subtree
This is a modified recursive strategy. When merging trees
A and B, if B corresponds to a subtree of A, B is first adjusted to match the
tree structure of A, instead of reading the trees at the same level. This
adjustment is also done to the common ancestor tree.
With the strategies that use 3-way merge (including the default,
recursive), if a change is made on both branches, but later reverted
on one of the branches, that change will be present in the merged result;
some people find this behavior confusing. It occurs because only the heads
and the merge base are considered when performing a merge, not the
individual commits. The merge algorithm therefore considers the reverted
change as no change at all, and substitutes the changed version instead.
CONFIGURATION¶
merge.conflictStyle
Specify the style in which conflicted hunks are written
out to working tree files upon merge. The default is "merge", which
shows a <<<<<<< conflict marker, changes made by
one side, a ======= marker, changes made by the other side, and then a
>>>>>>> marker. An alternate style,
"diff3", adds a ||||||| marker and the original text before
the ======= marker.
merge.defaultToUpstream
If merge is called without any commit argument, merge the
upstream branches configured for the current branch by using their last
observed values stored in their remote-tracking branches. The values of the
branch.<current branch>.merge that name the branches at the
remote named by branch.<current branch>.remote are consulted, and
then they are mapped via remote.<remote>.fetch to their
corresponding remote-tracking branches, and the tips of these tracking
branches are merged.
merge.ff
By default, Git does not create an extra merge commit
when merging a commit that is a descendant of the current commit. Instead, the
tip of the current branch is fast-forwarded. When set to false, this
variable tells Git to create an extra merge commit in such a case (equivalent
to giving the --no-ff option from the command line). When set to
only, only such fast-forward merges are allowed (equivalent to giving
the --ff-only option from the command line).
merge.verifySignatures
If true, this is equivalent to the --verify-signatures
command line option. See
git-merge(1) for details.
merge.branchdesc
In addition to branch names, populate the log message
with the branch description text associated with them. Defaults to
false.
merge.log
In addition to branch names, populate the log message
with at most the specified number of one-line descriptions from the actual
commits that are being merged. Defaults to false, and true is a synonym for
20.
merge.suppressDest
By adding a glob that matches the names of integration
branches to this multi-valued configuration variable, the default merge
message computed for merges into these integration branches will omit
"into <branch name>" from its title.
An element with an empty value can be used to clear the list of
globs accumulated from previous configuration entries. When there is no
merge.suppressDest variable defined, the default value of
master is used for backward compatibility.
merge.renameLimit
The number of files to consider when performing rename
detection during a merge; if not specified, defaults to the value of
diff.renameLimit. This setting has no effect if rename detection is turned
off.
merge.renames
Whether Git detects renames. If set to "false",
rename detection is disabled. If set to "true", basic rename
detection is enabled. Defaults to the value of diff.renames.
merge.directoryRenames
Whether Git detects directory renames, affecting what
happens at merge time to new files added to a directory on one side of history
when that directory was renamed on the other side of history. If
merge.directoryRenames is set to "false", directory rename detection
is disabled, meaning that such new files will be left behind in the old
directory. If set to "true", directory rename detection is enabled,
meaning that such new files will be moved into the new directory. If set to
"conflict", a conflict will be reported for such paths. If
merge.renames is false, merge.directoryRenames is ignored and treated as
false. Defaults to "conflict".
merge.renormalize
Tell Git that canonical representation of files in the
repository has changed over time (e.g. earlier commits record text files with
CRLF line endings, but recent ones use LF line endings). In such a repository,
Git can convert the data recorded in commits to a canonical form before
performing a merge to reduce unnecessary conflicts. For more information, see
section "Merging branches with differing checkin/checkout
attributes" in
gitattributes(5).
merge.stat
Whether to print the diffstat between ORIG_HEAD and the
merge result at the end of the merge. True by default.
merge.autoStash
When set to true, automatically create a temporary stash
entry before the operation begins, and apply it after the operation ends. This
means that you can run merge on a dirty worktree. However, use with care: the
final stash application after a successful merge might result in non-trivial
conflicts. This option can be overridden by the
--no-autostash and
--autostash options of
git-merge(1). Defaults to false.
merge.tool
Controls which merge tool is used by
git-mergetool(1). The list below shows the valid built-in values. Any
other value is treated as a custom merge tool and requires that a
corresponding mergetool.<tool>.cmd variable is defined.
merge.guitool
Controls which merge tool is used by
git-mergetool(1) when the -g/--gui flag is specified. The list below
shows the valid built-in values. Any other value is treated as a custom merge
tool and requires that a corresponding mergetool.<guitool>.cmd variable
is defined.
•araxis
•bc
•bc3
•codecompare
•deltawalker
•diffmerge
•diffuse
•ecmerge
•emerge
•examdiff
•guiffy
•gvimdiff
•gvimdiff2
•gvimdiff3
•kdiff3
•meld
•nvimdiff
•nvimdiff2
•nvimdiff3
•opendiff
•p4merge
•smerge
•tkdiff
•tortoisemerge
•vimdiff
•vimdiff2
•vimdiff3
•winmerge
•xxdiff
merge.verbosity
Controls the amount of output shown by the recursive
merge strategy. Level 0 outputs nothing except a final error message if
conflicts were detected. Level 1 outputs only conflicts, 2 outputs conflicts
and file changes. Level 5 and above outputs debugging information. The default
is level 2. Can be overridden by the GIT_MERGE_VERBOSITY environment
variable.
merge.<driver>.name
Defines a human-readable name for a custom low-level
merge driver. See
gitattributes(5) for details.
merge.<driver>.driver
Defines the command that implements a custom low-level
merge driver. See
gitattributes(5) for details.
merge.<driver>.recursive
Names a low-level merge driver to be used when performing
an internal merge between common ancestors. See
gitattributes(5) for
details.
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.
