pathspec: rename free_pathspec() to clear_pathspec()

The function takes a pointer to a pathspec structure, and releases
the resources held by it, but does not free() the structure itself.
Such a function should be called "clear", not "free".

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

builtin/update-index.c

@@ -759,7 +759,7 @@ static int do_reupdate(int ac, const char **av,
 		if (save_nr != active_nr)
 			goto redo;
 	}
-	free_pathspec(&pathspec);
+	clear_pathspec(&pathspec);
 	return 0;
 }