fsck-objects: work from subdirectory.

Not much point making it work from subdirectory, but for a
consistency make it so.

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

fsck-objects.c

@@ -431,6 +431,8 @@ int main(int argc, char **argv)
 {
 	int i, heads;
 
+	setup_git_directory();
+
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];