code: func (e *Runner) SetAdditionalFlags(fn func(*pflag.FlagSet)) {
  	// creates a new NewFlagSet
  	e.cmdAdditionalFlags = pflag.NewFlagSet("phaseAdditionalFlags", pflag.ContinueOnError)
  	// invokes the function that sets additional flags
  	fn(e.cmdAdditionalFlags)
  }
docs: // SetAdditionalFlags allows to define flags to be added
  // to the subcommands generated for each phase (but not existing in the parent command).
  // Please note that this command needs to be done before BindToCommand.
  // Nb. if a flag is used only by one phase, please consider using phase LocalFlags.