request-pull: really favor a matching tag

request-pull: really favor a matching tag

After tagging the tip of "dev" branch with a "for-linus" tag and
pushing both out, running

	$ git request-pull $url $last_release dev

would produce an output asking the 'dev' branch of $url to be
pulled, because that is what the user asked the message to say.

We already detect this situation locally and include the contents of
the tag in the output; if the $url has that tag, favor that tag
(i.e. "for-linus") in the generated message over the branch name the
user gave us (i.e. "dev") from the command line, to make the output
look more consistent.

Signed-off-by: Junio C Hamano <gitster@pobox.com>