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GIT-MERGE(1) | Git Manual | GIT-MERGE(1) |
NAME¶
git-merge - Join two or more development histories togetherSYNOPSIS¶
git merge [-n] [--stat] [--no-commit] [--squash] [--[no-]edit] [-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.A---B---C topic / D---E---F---G master
A---B---C topic / \ D---E---F---G---H master
OPTIONS¶
--commit, --no-commitPerform 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, --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
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.
--ff
When the merge resolves as a fast-forward,
only update the branch pointer, without creating a merge commit. This is the
default behavior.
--no-ff
Create a merge commit even when the merge
resolves as a fast-forward.
--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.
--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).
With --no-squash perform the merge and commit the result. This option can be
used to override --squash.
-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.
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.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.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. 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.
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.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.
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.
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.
•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:
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.
$ git merge --no-commit maint
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. resolveThis 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
octopus
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.
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.
renormalize
•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.
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.
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.
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.
CONFIGURATION¶
merge.conflictstyleSpecify 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.
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(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.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(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.
SEE ALSO¶
git-fmt-merge-msg(1), git-pull(1), gitattributes(5), 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) suite03/19/2016 | Git 1.7.10.4 |