git/Documentation/fetch-options.txt

-a, \--append::
	Append ref names and object names of fetched refs to the
	existing contents of `.git/FETCH_HEAD`.  Without this
	option old data in `.git/FETCH_HEAD` will be overwritten.

-f, \--force::
	When `git-fetch` is used with `<rbranch>:<lbranch>`
	refspec, it refuses to update the local branch
	`<lbranch>` unless the remote branch `<rbranch>` it
	fetches is a descendant of `<lbranch>`.  This option
	overrides that check.

\--no-tags::
	By default, `git-fetch` fetches tags that point at
	objects that are downloaded from the remote repository
	and stores them locally.  This option disables this
	automatic tag following.

-t, \--tags::
	Most of the tags are fetched automatically as branch
	heads are downloaded, but tags that do not point at
	objects reachable from the branch heads that are being
	tracked will not be fetched by this mechanism.  This
	flag lets all tags and their associated objects be
	downloaded.

-u, \--update-head-ok::
	By default `git-fetch` refuses to update the head which
	corresponds to the current branch.  This flag disables the
	check.  Note that fetching into the current branch will not
	update the index and working directory, so use it with care.