parse-remote: trivial fix to allow refs/{heads,tags}/ spelled easier.

Earlier we always prefixed refs/heads to the token given to "git fetch"
(and "git pull") as refspec.  This was a mistake.  Allow them to be
spelled like "master:refs/tags/paulus" to mean "I want to fetch the
master there and store it as my local "paulus" tag.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-parse-remote-script

@@ -81,10 +81,14 @@ canon_refs_list_for_fetch () {
 		local=$(expr "$ref" : '[^:]*:\(.*\)')
 		case "$remote" in
 		'') remote=HEAD ;;
+		refs/heads/* | refs/tags/*) ;;
+		heads/* | tags/* ) remote="refs/$remote" ;;
 		*) remote="refs/heads/$remote" ;;
 		esac
 		case "$local" in
 		'') local= ;;
+		refs/heads/* | refs/tags/*) ;;
+		heads/* | tags/* ) local="refs/$local" ;;
 		*) local="refs/heads/$local" ;;
 		esac
 		echo "${force}${remote}:${local}"