addHelpCommand(enableOrNameAndArgs, description) {
    if (enableOrNameAndArgs === false) {
      this._hasImplicitHelpCommand = false;
    } else {
      this._hasImplicitHelpCommand = true;
      if (typeof enableOrNameAndArgs === 'string') {
        this._helpCommandName = enableOrNameAndArgs.split(' ')[0];
        this._helpCommandnameAndArgs = enableOrNameAndArgs;
      }
      this._helpCommandDescription = description || this._helpCommandDescription;
    }
    return this;
  }
Override default decision whether to add implicit help command.

   addHelpCommand() // force on
   addHelpCommand(false); // force off
   addHelpCommand('help [cmd]', 'display help for [cmd]'); // force on with custom details

@return {Command} `this` command for chaining
@api public