parsedArgs._ contains all the arguments that didn't have an option associated
with them.
Numeric-looking arguments will be returned as numbers unless options.string or
options.boolean is set for that argument name.
Any arguments after '--' will not be parsed and will end up in parsedArgs._.
options can be:
options.string - a string or array of strings argument names to always treat
as strings.
options.boolean - a boolean, string or array of strings to always treat as
booleans. if true will treat all double hyphenated arguments without equal
signs as boolean (e.g. affects --foo, not -f or --foo=bar).
options.collect - a string or array of strings argument names to always
treat as arrays. Collectable options can be used multiple times. All values
will be collected into an array. If a non collectable option is used multiple
times, the last value is used. All Collectable arguments will be set to []
by default.
options.negatable - a string or array of strings argument names which can be
negated by prefixing them with --no-, like --no-config.
options.alias - an object mapping string names to strings or arrays of
string argument names to use as aliases.
options.default - an object mapping string argument names to default values.
options.stopEarly - when true, populate parsedArgs._ with everything after
the first non-option.
options['--'] - when true, populate parsedArgs._ with everything before
the -- and parsedArgs['--'] with everything after the --. Here's an
example:
options.unknown - a function which is invoked with a command line parameter
not defined in the options configuration object. If the function returns
false, the unknown option is not added to parsedArgs.