remove Argh/lean in favor of clap-only

[Byron]

cargo uses clap, so can we… it's not worth having multiple code paths for that and it's better to focus on one ultimate commandline arg parser rather than distribute efforts. It's possible to shrink clap for sure.

This is the foundation for fixing the long-standing issue of the progress being drawn after the program output was printed. The latter is already fixed for tui based progress, and the same solution should then work for the standard progress, too.

[oknozor]

Hey I would be interested to pick this issue, to get familiar with the code base. Do you want clap only or clap with structopt ?

[Byron]

Thanks for your interest! Maybe I can give you a boost with this illustration:

This issue isn't about implementing clap - it is available already - but removing the code path that uses argh. This work has already been performed for the porcelain CLI, but now needs to be done for the plumbing CLI as well.

I highly recommend following the collaboration guide, and if there are any additional questions, please let me know here or in the draft PR.

[oknozor]

Thank you, I will give it a shot.