GitHub Actions: Add separate hlint action

[slotThe]

Problem Description

Due to hlint's inconsistent packaging of releases it may be better to introduce a separate action for it. This would enable us to

• have more fine-grained control over the version that we use (e.g. in a situation like this we could just roll back to the last release),
• decouple the "hlint" step from the "does it work with some recent versions of GHC" step, which seems conceptually nicer.

For example, the haskell-language-server people seem to have already done this here

[ndmitchell]

The latest release of hlint now has a release binary.

[slotThe]

The latest release of hlint now has a release binary.

That's great news; thanks for the heads up!

[liskin]

I'll just note that the actions used in HLS CI are now part of the "official" Haskell GH Actions: https://github.com/haskell/actions/tree/main/hlint-setup, https://github.com/haskell/actions/tree/main/hlint-run so if this ever breaks again, we should try those.

[liskin]

Note that even with haskell-ci, we do have fine-grained control over the version we use, see 154388a#diff-eacabc2a664e928ef8b473245e842e4b29b9904fb1e4f64d565abbab93323e5cR12
So this really is only about the decoupling. Not sure if worth it, as we've been back to "just works" for a while.

[slotThe]

I didn't know about the hlint-version options, you're right that this is probably enough. Feel free to close if you don't think the decoupling is worth it

[liskin]

I just realized it's not just decoupling, but also that the https://github.com/haskell/actions/tree/main/hlint-run action produces annotations that GitHub understands and shows them directly in the PR diff. So this will likely be a quality-of-life improvement after all, and I'll leave this open then.

(I'll deal with xmonad/xmonad#401 and xmonad/xmonad#402 today but won't be spending any more time on hlint this weekend…)