mkdir (Archive::Tar::Minitar::Writer)

         # File lib/archive/tar/minitar.rb, line 394
    394:     def mkdir(name, opts = {})
    395:       raise ClosedStream if @closed
    396:       name, prefix = split_name(name)
    397:       header = { :name => name, :mode => opts[:mode], :typeflag => "5",
    398:                  :size => 0, :gid => opts[:gid], :uid => opts[:uid],
    399:                  :mtime => opts[:mtime], :prefix => prefix }
    400:       header = Archive::Tar::PosixHeader.new(header).to_s
    401:       @io.write(header)
    402:       nil
    403:     end