Ergonomics

[rye]

While I really do enjoy the idea of using git2 for performance, I think a far more economical and ergonomic approach is to just be a thin shell wrapper around git-checkout.

So, we might have behavior (e.g. which matcher to use: -s for Sublime, etc.) that needs to get configured via Clap, otherwise all arguments should get passed through.

Here are the changes to adopt:

• Use git-for-each-ref(1) for retrieving refnames (completions, search space) Use git2 for getting refs
• Use git-checkout(1) for actually checking things out.
• Any arguments preceding a -- are for us, the others are for git-checkout.

[rye]

I think once these are finished, this will be v1 ready.

[rye]

This will also resolve #7…