remove pathspec_match, use match_pathspec instead

Both versions have the same functionality. This removes any
redundancy.

This also adds makes two extensions to match_pathspec:

- If pathspec is NULL, return 1. This reflects the behavior of git
  commands, for which no paths usually means "match all paths".

- If seen is NULL, do not use it.

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-commit.c

@@ -166,7 +166,7 @@ static int list_paths(struct string_list *list, const char *with_tree,
 		struct cache_entry *ce = active_cache[i];
 		if (ce->ce_flags & CE_UPDATE)
 			continue;
-		if (!pathspec_match(pattern, m, ce->name, 0))
+		if (!match_pathspec(pattern, ce->name, ce_namelen(ce), 0, m))
 			continue;
 		string_list_insert(ce->name, list);
 	}