opts

type Opt interface {
	Name() string
	Short() string
	Help() string
	Default() reflect.Value
	Value() reflect.Value
	Item() Value
	FromEnv() bool
	EnvName() string
	HasSet() bool
}

type Opts interface {
	Parse() ParsedOpts
	Opts() []Opt
}

type ParsedOpts interface {
	//Help returns the final help text
	Help() string
	//IsRunnable returns whether the matched command has a Run method
	IsRunnable() bool
	//Run assumes the matched command is runnable and executes its Run method.
	//The target Run method must be 'Run() error' or 'Run()'
	Run() error
	//RunFatal assumes the matched command is runnable and executes its Run method.
	//However, any error will be printed, followed by an exit(1).
	RunFatal()
}

type Setter interface {
	Set(string) error
}

type Value interface {
	String() string
	Set(string) error
	Type() string
}