deprecate `BaseCommand`, merge into `Command`

[davidism]

As part of rewriting the parser in #2205, I was looking at the complexities of Click's definitions and processing. BaseCommand seems to exist to represent a command without the help, parse, and invoke behaviors implemented by Command. A test shows implementing parse_args to use optparse, where the parameters are defined there instead of as the command.params collection. This not documented, and subclassing Command instead doesn't prevent writing a custom parse_args method.

[davidism]

@janluke @kdeldycke any feedback on this is appreciated

[janluke]

A test shows implementing parse_args to use optparse, where the parameters are defined there instead of as the command.params collection.

I'm fine with the removal, especially if that's the only purpose of BaseCommand (using something different than command.params). Personally I've never made use of BaseCommand. In cloup I had a BaseCommand too but I quickly removed it because it didn't serve any purpose.

[kdeldycke]

Yes, same as @janluke, never had to use it and was quite confused by its existence. Nothing prevent merging that back to Command.

So yes, I agree BaseCommand could be removed. 👍