@nmeilick , I have sloved this issue and submited RP.

Solution Approach :

• Add an new option ShowDefaultValue in BoolFlag
• If ShowDefaultValue option is true then print default value or if false then it does not print.

Modified files :

1. flag_bool.go
2. flag.go
3. app_test.go

Before Changes :

func stringifyFlag(f Flag) string {
	fv := flagValue(f)

	switch f := f.(type) {
	case *IntSliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyIntSliceFlag(f))
	case *Int64SliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyInt64SliceFlag(f))
	case *Float64SliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyFloat64SliceFlag(f))
	case *StringSliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyStringSliceFlag(f))
	}

	placeholder, usage := unquoteUsage(fv.FieldByName("Usage").String())

	needsPlaceholder := false
	defaultValueString := ""
	val := fv.FieldByName("Value")
	if val.IsValid() {
		needsPlaceholder = val.Kind() != reflect.Bool
		defaultValueString = fmt.Sprintf(formatDefault("%v"), val.Interface())
		if val.Kind() == reflect.String && val.String() != "" {
			defaultValueString = fmt.Sprintf(formatDefault("%q"), val.String())
		}
	}

	helpText := fv.FieldByName("DefaultText")
	if helpText.IsValid() && helpText.String() != "" {
		needsPlaceholder = val.Kind() != reflect.Bool
		defaultValueString = fmt.Sprintf(formatDefault("%s"), helpText.String())
	}

	if defaultValueString == formatDefault("") {
		defaultValueString = ""
	}

	if needsPlaceholder && placeholder == "" {
		placeholder = defaultPlaceholder
	}

	usageWithDefault := strings.TrimSpace(usage + defaultValueString)

	return withEnvHint(flagStringSliceField(f, "EnvVars"),
		fmt.Sprintf("%s\t%s", prefixedNames(f.Names(), placeholder), usageWithDefault))
}

After changes :

func stringifyFlag(f Flag) string {
	fv := flagValue(f)

	switch f := f.(type) {
	case *IntSliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyIntSliceFlag(f))
	case *Int64SliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyInt64SliceFlag(f))
	case *Float64SliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyFloat64SliceFlag(f))
	case *StringSliceFlag:
		return withEnvHint(flagStringSliceField(f, "EnvVars"),
			stringifyStringSliceFlag(f))
	}

	placeholder, usage := unquoteUsage(fv.FieldByName("Usage").String())

	needsPlaceholder := false
	defaultValueString := ""
	val := fv.FieldByName("Value")
	showDefaultValue := fv.FieldByName("ShowDefaultValue")
	if val.IsValid() {
		needsPlaceholder = val.Kind() != reflect.Bool
		defaultValueString = fmt.Sprintf(formatDefault("%v"), val.Interface())
		if val.Kind() == reflect.Bool && !showDefaultValue.Bool() {
			defaultValueString = ""
		}
		if val.Kind() == reflect.String && val.String() != "" {
			defaultValueString = fmt.Sprintf(formatDefault("%q"), val.String())
		}
	}

	helpText := fv.FieldByName("DefaultText")
	if helpText.IsValid() && helpText.String() != "" {
		needsPlaceholder = val.Kind() != reflect.Bool
		defaultValueString = fmt.Sprintf(formatDefault("%s"), helpText.String())
		if val.Kind() == reflect.Bool && !showDefaultValue.Bool() {
			defaultValueString = ""
		}
	}

	if defaultValueString == formatDefault("") {
		defaultValueString = ""
	}

	if needsPlaceholder && placeholder == "" {
		placeholder = defaultPlaceholder
	}

	usageWithDefault := strings.TrimSpace(usage + defaultValueString)

	return withEnvHint(flagStringSliceField(f, "EnvVars"),
		fmt.Sprintf("%s\t%s", prefixedNames(f.Names(), placeholder), usageWithDefault))
}

I put this same comment on the PR for the BoolFlag, but putting it here for additional context/discussion.

Throwing this out there, it would be really nice if the ShowDefaultValue parameter existed for other options too. The reason I'm asking is because in a situation where a CLI app is picking up configuration from an environmental variable, it's too easy to accidentally expose that information.

I've got a situation where I'm using this library to create a containerized plugin for use within a CI environment, and it will get injected secrets through way of env variables, but if the user malforms their configuration, any of the set secrets will be exposed by the help menu. For now I'm just setting DefaultText to N/A so it doesn't appear, but this param would be nice to exist on all available flags.