# File lib/mercenary/command.rb, line 73
    def default_command(command_name = nil)
      if command_name
        if commands.has_key?(command_name)
          @default_command = commands[command_name] if command_name
          @default_command
        else
          raise ArgumentError.new("'#{command_name}' couldn't be found in this command's list of commands.")
        end
      else
        @default_command
      end
    end