Expose metadata for test assertions

[dyc3]

I would like to be able to write unit tests for some of Biome's args. Things like "all arguments for this struct must have this prefix in the name" and "all arguments must not have a short version of the arg". And I'd like to do it in a way that doesn't require writing a bunch of unit tests, and I'd like for those tests to remain valid if arguments are added or removed.

Currently, this is technically possible via regexing generated help text I suppose. But it would be nice to be able to access the metadata anyway.

[pacak]

Right now I'm working on the next version that addresses some of the annoyances - having to specify positional items at the right most end is one of them, but some other items as well (#406). Developer facing API should stay the same except for some small corner cases. It is still some time away though. I already replaced metadata system with a visitor based approach and I'm planning to make it a part of the public API.

So... A month or two? Anything else on your wish list BTW?

[dyc3]

If I think of anything I'll let you know. Thank you!