class Gem::Package::TarWriter

def mkdir(name, mode)
  check_closed
  name, prefix = split_name(name)
  header = Gem::Package::TarHeader.new :name => name, :mode => mode,
                                       :typeflag => "5", :size => 0,
                                       :prefix => prefix,
                                       :mtime => Time.now
  @io.write header
  self
end