v0.22.0: Breaking Change

As the releases before, this release has 100% test coverage.
Tested with Go 1.14 and Go 1.15.

Bug fix

Fix completion issues where a completion that works when starting to complete from scratch fails when some args are deleted.

Fixed by changing the exit status when generating completions from 1 to 124.
Exit 124 means programmable completion restarts from the beginning, with an attempt to find a new compspec for that command.

Feature Removal

Removing negatable flags NBool and NBoolVar.
A feature that adds a bunch of complexity for very little value and prevents reading environment variables into booleans.

New Features

• opt.GetEnv Is now supported when using opt.Bool and opt.BoolVar.
  Previously only opt.String and opt.StringVar were supported.

  When using opt.GetEnv with opt.Bool or opt.BoolVar, only the words "true" or "false" are valid.
  They can be provided in any casing, for example: "true", "True" or "TRUE".

• opt.Dispatch now automatically handles the help flag.
  The help flag needs to be defined at the top level.
  When the help flag is called and handled by a command opt.Dispatch now returns an error of type getoptions.ErrorHelpCalled.

  For example:

func main() {
	os.Exit(program())
}

func program() int {
	opt := getoptions.New()
	opt.Bool("help", false, opt.Alias("?"))    // Define the help flag as "--help" with alias "-?"
	list := opt.NewCommand("list", "list stuff").SetCommandFn(listRun)
	list.Bool("list-opt", false)
	opt.HelpCommand("")
	remaining, err := opt.Parse(os.Args[1:])
	if err != nil {
		fmt.Fprintf(os.Stderr, "ERROR: %s\n", err)
		os.Exit(1)
	}

	ctx, cancel, done := opt.InterruptContext()
	defer func() { cancel(); <-done }()

	err = opt.Dispatch(ctx, "help", remaining) // Use the same help flag "help".
	if err != nil {
		if errors.Is(err, getoptions.ErrorHelpCalled) {
			return 1
		}
		fmt.Fprintf(os.Stderr, "ERROR: %s\n", err)
		return 1
	}
	return 0
}

Now, calling program list --help or program list -? prints the help for the list command as well as calling program help list.