In https://github.com/NixOS/hydra/pull/1549 diffs were
offloaded to github for performance reasons.
While in some endpoints github accepts `.git` suffixed in the
repository name, in the comparison endpoint this does not seem
to be the case.
Specifically, on the main nixos org hydra this isn't working:
Example job: https://hydra.nixos.org/build/320178054
Generates a comparison link like so:
078d69f039...1cd347bf33
This just stips away the suffix and seems to work fine in local
testing.
26e4d5eb54