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>]


        [--into-name <branch>] [<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. Before the operation, ORIG_HEAD is set to the tip of the current branch (C).

          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

--edit, -e, --no-edit

--cleanup=<mode>

--ff, --no-ff, --ff-only

-S[<keyid>], --gpg-sign[=<keyid>], --no-gpg-sign

--log[=<n>], --no-log

--signoff, --no-signoff

--stat, -n, --no-stat

--squash, --no-squash

--[no-]verify

-s <strategy>, --strategy=<strategy>

-X <option>, --strategy-option=<option>

--verify-signatures, --no-verify-signatures

--summary, --no-summary

-q, --quiet

-v, --verbose

--progress, --no-progress

--autostash, --no-autostash

--allow-unrelated-histories

-m <msg>

--into-name <branch>

-F <file>, --file=<file>

--rerere-autoupdate, --no-rerere-autoupdate

--overwrite-ignore, --no-overwrite-ignore

--abort

--quit

--continue

<commit>...

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:

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,
or cleanly resolved because both sides changed the same way.
<<<<<<< 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 either "diff3" or "zdiff3". 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
or cleanly resolved because both sides changed the same way.
Conflict resolution is hard;
let's go shopping.
||||||| base:sample.txt
or cleanly resolved because both sides changed identically.
Conflict resolution is hard.
=======
or cleanly resolved because both sides changed the same way.
Git makes conflict resolution easy.
>>>>>>> theirs:sample.txt
And here is another line that is cleanly resolved or unmodified.

while in "zdiff3" style, it may look like this:

Here are lines that are either unchanged from the common
ancestor, or cleanly resolved because only one side changed,
or cleanly resolved because both sides changed the same way.
<<<<<<< yours:sample.txt
Conflict resolution is hard;
let's go shopping.
||||||| base:sample.txt
or cleanly resolved because both sides changed identically.
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:

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

EXAMPLES¶

$ git merge fixes enhancements

$ git merge -s ours obsolete

$ 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.

ort

recursive

resolve

octopus

ours

subtree

With the strategies that use 3-way merge (including the default, ort), 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¶

branch.<name>.mergeOptions

Everything above this line in this section isn’t included from the git-config(1) documentation. The content that follows is the same as what’s found there:

merge.conflictStyle

merge.defaultToUpstream

merge.ff

merge.verifySignatures

merge.branchdesc

merge.log

merge.suppressDest

merge.renameLimit

merge.renames

merge.directoryRenames

merge.renormalize

merge.stat

merge.autoStash

merge.tool

merge.guitool

merge.verbosity

merge.<driver>.name

merge.<driver>.driver

merge.<driver>.recursive

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) suite