Before this, the tool for CI would update when nixos-unstable updated,
which is kind of terrible because you don't know when it happens, and it
might break master.
In fact, the tooling _right now_ has a serious bug and shouldn't be used!
This PR addresses this by _pinning_ the tooling in Nixpkgs itself.
Updating the tooling now requires two PRs:
- The first PR to update the tooling source
- (wait for Hydra to build and publish it in nixos-unstable)
- The second PR to update the pinned tooling
In turn you know exactly when the changes are going to take effect.
This change however has additional benefits:
- It makes CI more reproducible, because it doesn't depend on the state
of nixos-unstable anymore
- Updates to the tooling can be tested with the workflow itself,
because PRs that update the pinned tool will be tested on the updated
version
- CI gets a sizable speed boost, because there's no need to download and
evaluate a channel anymore
- It makes it more realistic to move the source of the tool into a
separate repository
- It removes the brittle branch-specific logic that was previously
needed to ensure that release branches use their own version of the
tooling.
cc422e321e