argument_parser

type ExclusiveGroup struct {
	Options []option.Option
	// Required demands that one of them be given.
	Required bool
}

type Group struct {
	Title   string
	Options []option.Option
}

type Parser struct {
	Options []option.Option
	Parsers []Subparser
	// Groups arrange options under their own headings in the help message. An option that appears
	// in no group is listed under "Options:".
	Groups []*Group
	// ExclusiveGroups declare options that rule one another out.
	ExclusiveGroups []*ExclusiveGroup
	// Command is the name this parser answers to when it is used as a Subparser.
	Command     string
	Description string
	ProgramName string
	// Positionals are given the arguments that name no option, in order, according to how many
	// each takes. A positional is named in the help by its metavar.
	Positionals []option.Option
	// Rest receives the arguments left over once the positionals have taken theirs, including
	// everything after a "--" terminator. A leftover argument is an error while this is nil.
	Rest *[]string
	// DisableHelp withholds the automatic help option, leaving "-h" and "--help" to be used as
	// ordinary option names, or to be reported as unknown.
	DisableHelp bool
	// DisableAbbrev withholds prefix matching of long names. It is allowed by default, as argparse
	// and getopt_long allow it: an unambiguous prefix stands for the whole name, and an ambiguous
	// one is an error naming the candidates. Disabling it fixes the accepted command line to the
	// names as written, so that adding an option later cannot break a caller that spelled an
	// existing one short.
	DisableAbbrev bool
	// Output receives the help message. os.Stdout is used when nil: help is an answer to an
	// explicit request, not a diagnostic, so it must stay on stdout to survive a pipe.
	Output io.Writer
	// Width is the column at which the help message wraps. COLUMNS, then defaultWidth, is used
	// when this is not positive.
	Width int
}

type Subparser interface {
	ParseArgs([]string) error
	GetCommand() string
}