+my @old = PublicInbox::Admin::resolve_inboxes([$old_dir], undef, $cfg);
+@old > 1 and die "BUG: resolved several inboxes from $old_dir:\n",
+ map { "\t$_->{inboxdir}\n" } @old;
+my $old = PublicInbox::InboxWritable->new($old[0]);
+if (delete $old->{-unconfigured}) {