Refactor find_non_local_tags and get_ref_map to only take the
information they need instead of the entire transport struct. Besides
improving code clarity, this also improves their flexibility, allowing
for a different set of refs to be used instead of relying on the ones
stored in the transport struct.
Signed-off-by: Brandon Williams <bmwill@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>