Documentation/merge-options.txt

--summary::
	Show a diffstat at the end of the merge. The diffstat is also
	controlled by the configuration option merge.diffstat.

-n, \--no-summary::
	Do not show diffstat at the end of the merge.

--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.

--commit::
	Perform the merge and commit the result. This option can
	be used to override --no-commit.

--squash::
	Produce the working tree and index state as if a real
	merge happened, 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).

--no-squash::
	Perform the merge and commit the result. This option can
	be used to override --squash.

--no-ff::
	Generate a merge commit even if the merge resolved as a
	fast-forward.

--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.

-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).