Replace parser with System.CommandLine

[natemcmaster]

The .NET team is working on creating a parsing library tentatively called System.CommandLine. See https://github.com/dotnet/command-line-api.

I am considering replacing the parser in this library with System.CommandLine. It would be a substantial breaking change, but this parser has a much richer API for parsing along with some other nice features that I don't want to re-invent on my own.

This change needs more investigation.

[atruskie]

FWIW part of the reason i chose this library was because it was an adaptation of System.CommandLine. I was hoping if they finished work in System.CommandLine then the delta between my app and the standard impl would be smaller. So 👍

[TheConstructor]

So I guess this depends in part on dotnet/command-line-api#356. What will this project become? Configuration-infrastructure (I believe they currently don't have annotation support) and helpers?

I know it says needs-design and breaking-change, but I am really interested how deep and how far you plan this to go.

[natemcmaster]

I gave this some more thought over the last few weeks. At this point, I'm not planning to make this change. (see also #206 for my thoughts on what will become of this project)