GIT-MERGE(1)                                                      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:


       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.


       --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).

              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.

              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 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&#8217;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
       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&#8217;s remark on your side. The only thing you
       can tell is that your side wants to say it is hard and you&#8217;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. 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.

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.


              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(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.


       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.


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.


       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) suite




                                                                  GIT-MERGE(1)
