class Gem::Commands::UpdateCommand

def update_rubygems
  if Gem.disable_system_update_message
    alert_error Gem.disable_system_update_message
    terminate_interaction 1
  end
  check_update_arguments
  version, requirement = rubygems_target_version
  check_latest_rubygems version
  check_oldest_rubygems version
  installed_gems = Gem::Specification.find_all_by_name "rubygems-update", requirement
  installed_gems = update_gem("rubygems-update", requirement) if installed_gems.empty? || installed_gems.first.version != version
  return if installed_gems.empty?
  install_rubygems installed_gems.first
end