tar-tree: finish honoring extractor's umask in git-tar-tree.

Earlier commit 38ec15a973 forgot
to apply the same principle of not forcing go-w to the base
directory when specified.

Signed-off-by: Junio C Hamano <junkio@cox.net>

tar-tree.c

@@ -433,7 +433,7 @@ int main(int argc, char **argv)
 		archive_time = time(NULL);
 	if (basedir)
 		write_header((unsigned char *)"0", TYPEFLAG_DIR, NULL, NULL,
-			basedir, 040755, NULL, 0);
+			basedir, 040777, NULL, 0);
 	traverse_tree(buffer, size, NULL);
 	free(buffer);
 	write_trailer();