sub add_to_tar {
        my($tar, $thing, $base) = @_;

        if (defined $base) {
            chdir $base or die "Can't chdir to $base: $!";
            $thing =~ s!^$base/?!!;
        }

        if (-f $thing) {
            $tar->add_files($thing);
        }
        elsif (-d $thing) {
            my $code = sub {
                return if !-f $_;

                local *FH;
                open FH, $_ or die "Can't open $_: $!";
                binmode FH;
                my $c = do { local $/; <FH> };
                close FH or die "Can't close $_: $!";

                $tar->add_data($File::Find::name, $c);
            };
            find $code, $thing;
        }
    }