largefiles: unlink standins not known to the restored dirstate at rollback Before this patch, standinds not known to the restored dirstate at rollback still exist after rollback of the parent of the working directory, and they become orphans unexpectedly. This patch unlinks standins not known to the restored dirstate. This patch saves names of standins matched against not "repo.dirstate[f] == 'a'" but "repo.dirstate[f] != 'r'" before rollback, because branch merging marks files newly added to dirstate as not "a" but "n". Such standins will also become orphan after rollback, because they are not known to the restored dirstate.