Add it blame-copy-royal

[cruessler]

This is a draft PR. It is mostly intended for early feedback, in case there’s any. I plan on addressing the remaining TODOs over the course of the coming days. I also plan on providing more context. :-)

[Byron]

Thanks for making this happen!

Early feedback could be that this seems to be a breaking change in gix-blame, which should then go into a separate commit. I didn't look at it beyond that though.

[cruessler]

@Byron I think I’ve now reached a point where it makes sense for you to start reviewing!

I tried to add as much context as possible in comments. I hope that’s enough context, let me know if you need more! I also tried to have each commit only touch a single crate. Feel free to squash if you want!

What I wasn’t sure about was the command’s name. This initial version basically just copies the name from copy-royal because it seems somehow related. Another option that might work is extract-blame-history.

I will continue testing the PR in the background. My gut feeling tells me that, at this point, any issues I might still find could also be issues in the blame implementation itself.