go/src/cmd/go/internal/cmdflag/flag.go

var ErrFlagTerminator …

type FlagNotDefinedError …

func (e FlagNotDefinedError) Error() string { … }

type NonFlagError …

func (e NonFlagError) Error() string { … }

// ParseOne sees if args[0] is present in the given flag set and if so,
// sets its value and returns the flag along with the remaining (unused) arguments.
//
// ParseOne always returns either a non-nil Flag or a non-nil error,
// and always consumes at least one argument (even on error).
//
// Unlike (*flag.FlagSet).Parse, ParseOne does not log its own errors.
func ParseOne(fs *flag.FlagSet, args []string) (f *flag.Flag, remainingArgs []string, err error) { … }

type boolFlag …