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/reset.c

@@ -158,7 +158,7 @@ static int read_from_tree(const struct pathspec *pathspec,
 		return 1;
 	diffcore_std(&opt);
 	diff_flush(&opt);
-	free_pathspec(&opt.pathspec);
+	clear_pathspec(&opt.pathspec);
 
 	return 0;
 }