sub list_files {
  my ($self, $dir) = @_;

  # Files relative to directory
  my $parts = $self->{parts} || [];
  my $root = File::Spec->catdir(@$parts);
  $dir = File::Spec->catdir($root, split '/', ($dir || ''));
  return [] unless -d $dir;
  my @files;
  find {
    no_chdir => 1,
    wanted =>
      sub { push @files, File::Spec->abs2rel($File::Find::name, $dir) }
    },
    $dir;

  return [sort @files];
}