Allow to declare options about claide

[segiddins]

👍🏻 just thought of a cool, totally backwards-compatible way to do this. Will throw up a PR once this play is over.

[segiddins]

How would you then remove an option in s subclass?

[mrackwitz]

I could imagine different ways to achieve that.

A: Don't add them in the first place. The interface would be much more composable. So universal subclasses don't necessarily need to define optional options for subclasses and could put them into separate modules.

B: This could be backwards-compatible with the current API. The declared options could be appended to a class variable declared_options, which could be an input to self.options. The latter would still host only an array of pairs with names and descriptions. If an option is removed from the UI, it won't be parsed in later steps. The implicitly defined accessors would be likely still available in that case, which could lead to programmer errors.

C: Class-based option black-listing.

class AeroPress < CoffeeMaker
    self.remove_option '--[no-]milk'
    self.remove_option ['--sweetner', '-s']
end