t5510: prepare test refs more straightforwardly
"git fetch" was being used with contrived refspecs to create tags and
remote-tracking branches in test repositories in preparation for the
actual tests. This is obscure and also makes one wonder whether this
is indeed just preparation or whether some side-effect of "git fetch"
is being tested.
So use the more straightforward commands "git tag" / "git update-ref"
when preparing branches in test repositories.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>