`haskell-ci` problems

[silas-hw]

The cache is heavily polluted by haskell-ci, and it seems it always saves a new cache every commit even if restoring from an older one and not changing anything in it.

Also, does it need to be testing on so many GHC versions? After discussing with @TOTBWF, it seems we could cut down the matrix a lot.

[JacquesCarette]

Our matrix should track that of Agda 2.9. There is no point in testing more versions than that, really.

[jamesmckinna]

Hmmm. When you say "Agda 2.9", you mean the current master branch of agda?
In which case, for the sake of avoiding easily-avoidable regressions:

• test against master
• test against the last previous release version?

[gallais]

haskell-ci is about ghc & cabal, not Agda. Jacques means we should be testing against the
same pairs of ghc & cabal versions that Agda supports; no point in going back further in time.

[silas-hw]

Does the patch file ever get applied to the workflow file? If it needs to be manually done, it seems it's been missed, and hence the workflow is always being triggered.

Fixing this would reduce cache usage a lot itself.