command :open do |c|
  c.syntax = 'rubychina open [SESSION]'
  c.summary = 'Open your browser to the ruby-china to view topic'
  c.description = ''

  c.action do |args, options|
    say_error "Missing topic number" and abort unless @number = (Integer(args.first) rescue nil)
    `open http://ruby-china.org/topics/#{@number}`
  end
end