Command

Arguments are expanded then parsed. By default, argument expansion is the identity function. Overriding this method allows plugging in an arbitrary argument expansion logic.

One such expansion logic involves replacing each argument of the form '@' with the contents of that file where each line in the file becomes a distinct argument. To enable this behavior, override this method as shown below.

Whether to ignore unrecognized arguments.

That is, if there are unrecognized arguments, the parsing still succeeds. The unparsed arguments are put in the args argument of run.

Whether to stop parsing at the first unrecognized argument.

That is, stop parsing at the first non option (not starting with "-"), or the first unrecognized option. The unparsed arguments are put in the args argument of run.