# File lib/rubygems/commands/update_command.rb, line 137
  def do_rubygems_update(version)
    args = []
    args.push '--prefix', Gem.prefix unless Gem.prefix.nil?
    args << '--no-rdoc' unless options[:generate_rdoc]
    args << '--no-ri' unless options[:generate_ri]
    args << '--no-format-executable' if options[:no_format_executable]

    update_dir = File.join Gem.dir, 'gems', "rubygems-update-#{version}"

    Dir.chdir update_dir do
      say "Installing RubyGems #{version}"
      setup_cmd = "#{Gem.ruby} setup.rb #{args.join ' '}"

      # Make sure old rubygems isn't loaded
      old = ENV["RUBYOPT"]
      ENV.delete("RUBYOPT")
      system setup_cmd
      ENV["RUBYOPT"] = old if old
    end
  end