class Gem::Commands::UpdateCommand

def update_rubygems
  unless options[:args].empty? then
    alert_error "Gem names are not allowed with the --system option"
    terminate_interaction 1
  end
  options[:user_install] = false
  # TODO: rename version and other variable name conflicts
  # TODO: get rid of all this indirection on name and other BS
  version = options[:system]
  if version == true then
    version     = Gem::Version.new     Gem::VERSION
    requirement = Gem::Requirement.new ">= #{Gem::VERSION}"
  else
    version     = Gem::Version.new     version
    requirement = Gem::Requirement.new version
  end
  rubygems_update         = Gem::Specification.new
  rubygems_update.name    = 'rubygems-update'
  rubygems_update.version = version
  hig = {
    'rubygems-update' => rubygems_update
  }
  gems_to_update = which_to_update hig, options[:args], :system
  name, up_ver   = gems_to_update.first
  current_ver    = Gem::Version.new Gem::VERSION
  target = if options[:system] == true then
             up_ver
           else
             version
           end
  if current_ver == target then
    # if options[:system] != true and version == current_ver then
    say "Latest version currently installed. Aborting."
    terminate_interaction
  end
  update_gem name, target
  installed_gems = Gem::Specification.find_all_by_name 'rubygems-update', requirement
  version        = installed_gems.last.version
  args = []
  args << '--prefix' << Gem.prefix if Gem.prefix
  # TODO use --document for >= 1.9 , --no-rdoc --no-ri < 1.9
  args << '--no-rdoc' unless options[:document].include? 'rdoc'
  args << '--no-ri'   unless options[:document].include? '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") if old
    installed = system setup_cmd
    say "RubyGems system software updated" if installed
    ENV["RUBYOPT"] = old if old
  end
end