bundle: allow the same ref to be given more than once

"git bundle create x master master" used to create a bundle that lists
the same branch (master) twice.  Cloning from such a bundle resulted in
a needless warning "warning: Duplicated ref: refs/remotes/origin/master".

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

bundle.c

@@ -240,6 +240,8 @@ int create_bundle(struct bundle_header *header, const char *path,
 		return error("unrecognized argument: %s'", argv[i]);
 	}
 
+	object_array_remove_duplicates(&revs.pending);
+
 	for (i = 0; i < revs.pending.nr; i++) {
 		struct object_array_entry *e = revs.pending.objects + i;
 		unsigned char sha1[20];