link_temp_to_file: don't leave the path truncated on adjust_shared_perm failure

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

sha1_file.c

@@ -1383,8 +1383,10 @@ static int link_temp_to_file(const char *tmpfile, const char *filename)
 	if (dir) {
 		*dir = 0;
 		mkdir(filename, 0777);
-		if (adjust_shared_perm(filename))
+		if (adjust_shared_perm(filename)) {
+			*dir = '/';
 			return -2;
+		}
 		*dir = '/';
 		if (!link(tmpfile, filename))
 			return 0;