def cmd_rnfr(param)
      send_unauthorised and return unless logged_in?
      send_param_required and return if param.nil?

      @from_filename = build_path(param)
      send_response "350 Requested file action pending further information."
    end
def cmd_rnfr(param)
      send_unauthorised and return unless logged_in?
      send_param_required and return if param.nil?

      @from_filename = build_path(param)
      send_response "350 Requested file action pending further information."
    end
rename a file