add branch command (draft)

[milahu]

fix #271

mostly copy-paste of the pr command

• parser for branch urls
• function review.build_branch(branch)
• tests
• maybe refactor with the pr command

[Mic92]

Implementation looks good so far. As you already put it out a test would be nice and also documentation in the README.

[milahu]

6fe1fee fixes my caller error

nix-review rev -r https://github.com/delroth/nixpkgs -b gstreamermm-build-fix a9f5b7dbfe16c81a026946f2c9931479be31171d

because the branch gstreamermm-build-fix is a9f5b7dbfe16c81a026946f2c9931479be31171d

also there is a bug in rev. when i call

nix-review rev -r https://github.com/delroth/nixpkgs a9f5b7dbfe16c81a026946f2c9931479be31171d

then nix-review fetches the master branch of https://github.com/delroth/nixpkgs but the fork is out-of-sync with NixOS/nixpkgs, so as base commit i get delroth/nixpkgs@045a4a4 (2018-10-13)

nix-review should get the ahead status of the branch, to find the base commit delroth/nixpkgs@19e187f (2022-05-05)
see stackoverflow: git ahead behind info

[milahu]

now this works

nixpkgs-review branch https://github.com/milahu/nixpkgs/tree/qt6-631 -C ~/nixpkgs

this PR still needs some polish ...

[Mic92]

I would prefer to have no dependencies outside the python stdlib in nixpkgs-review. There is for example: https://docs.python.org/3/library/dbm.html and one could just keep the last 100 evals...

[milahu]

eval cache is now a "stupid file cache" with *.xml.gz files (todo: garbage collect)

i think it's useful and stable enough to make eval-cache default on