def mkdir(dir)
      unless in_zip?
        FileUtils.mkdir_p current_dir.join(dir)
      else
        Zip::File.open(current_zip) do |zip|
          zip.dir.mkdir dir
        end
      end
      ls
    end
def mkdir(dir)
      unless in_zip?
        FileUtils.mkdir_p current_dir.join(dir)
      else
        Zip::File.open(current_zip) do |zip|
          zip.dir.mkdir dir
        end
      end
      ls
    end
Create a new directory.