fetch: allow "git fetch $there v1.0" to fetch a tag

You can already do so with "git fetch $there tags/v1.0" but if it is not
ambiguous there is no reason to force users to type more.

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

refs.c

@@ -998,6 +998,7 @@ const char *ref_rev_parse_rules[] = {
 const char *ref_fetch_rules[] = {
 	"%.*s",
 	"refs/%.*s",
+	"refs/tags/%.*s",
 	"refs/heads/%.*s",
 	NULL
 };