git-merge
(1)
Name
git-merge - Join two or more development histories together
Synopsis
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
Git Manual GIT-MERGE(1)
NAME
git-merge - Join two or more development histories together
SYNOPSIS
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
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:
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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
--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 but pretend the merge
failed and do not autocommit, to give the user a chance
to inspect and further tweak the merge result before
committing.
--edit, -e
Invoke editor before committing successful merge to
further edit the default merge message.
--ff, --no-ff
Do not generate a merge commit if the merge resolved as
a fast-forward, only update the branch pointer. This is
the default behavior of git-merge.
With --no-ff Generate a merge commit even if the merge
resolved as a fast-forward.
--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.
--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 or move the HEAD, nor
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).
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With --no-squash perform the merge and commit the
result. This option can be used to override --squash.
--ff-only
Refuse to merge and exit with a non-zero status unless
the current HEAD is already up-to-date or the merge can
be resolved as a fast-forward.
-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.
--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.
-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.
--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.
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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 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
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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.
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
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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:
o Decide not to merge. The only clean-ups you need are to
reset the index file to the HEAD commit to reverse 2.
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and to clean up working tree changes made by 2. and 3.;
git merge --abort can be used for this.
o 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:
o Use a mergetool. git mergetool to launch a graphical
mergetool which will work you through the merge.
o Look at the diffs. git diff will show a three-way diff,
highlighting changes from both the HEAD and MERGE_HEAD
versions.
o 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.
o 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
o Merge branches fixes and enhancements on top of the
current branch, making an octopus merge:
$ git merge fixes enhancements
o Merge branch obsolete into the current branch, using
ours merge strategy:
$ git merge -s ours obsolete
o 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.
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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 mis-merges by tests done on actual merge commits
taken from Linux 2.6 kernel development history.
Additionally this can detect and handle merges involving
renames. 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 to the merge result.
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 opposite of ours.
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.
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ignore-space-change, ignore-all-space,
ignore-space-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, and --ignore-space-at-eol.
o If their version only introduces whitespace
changes to a line, our version is used;
o If our version introduces whitespace changes but
their version includes a substantial change,
their version is used;
o 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(4) for details.
no-renormalize
Disables the renormalize option. This overrides the
merge.renormalize configuration variable.
rename-threshold=<n>
Controls the similarity threshold used for rename
detection. See also git-diff(1) -M.
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
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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.
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.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.
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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.
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(4).
merge.stat
Whether to print the diffstat between ORIG_HEAD and the
merge result at the end of the merge. True by default.
merge.tool
Controls which merge resolution program is used by git-
mergetool(1). Valid built-in values are: "araxis",
"bc3", "diffuse", "ecmerge", "emerge", "gvimdiff",
"kdiff3", "meld", "opendiff", "p4merge", "tkdiff",
"tortoisemerge", "vimdiff" and "xxdiff". Any other value
is treated is custom merge tool and there must be a
corresponding mergetool.<tool>.cmd option.
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(4) for details.
merge.<driver>.driver
Defines the command that implements a custom low-level
merge driver. See gitattributes(4) for details.
merge.<driver>.recursive
Names a low-level merge driver to be used when
performing an internal merge between common ancestors.
See gitattributes(4) for details.
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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.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | developer/versioning/git |
+---------------+--------------------------+
|Stability | Uncommitted |
+---------------+--------------------------+
SEE ALSO
git-fmt-merge-msg(1), git-pull(1), gitattributes(4), git-
reset(1), git-diff(1), git-ls-files(1), git-add(1), git-
rm(1), git-mergetool(1)
GIT
Part of the git(1) suite
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from http://git-
core.googlecode.com/files/git-1.7.9.2.tar.gz
Further information about this software can be found on the
open source community website at http://git-scm.com/.
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