Tidy ci.nix using dimension

[michaelpj]

I recently came across this rather nice way of structuring build
matrices for ci.nix.

I think it makes the haskell.nix ci.nix a lot clearer!

[michaelpj]

Weirdly, this is much more green than the normal runs, I think because I'm not aggressively recursing into haskellNixRoots the way the old one did. I think we probably shouldn't be doing that: if you're supposed to evaluate all that stuff for haskellNixRoots, then it should have recurseForDerivation set inside it appropriately.

[angerman]

This looks awesome!

[angerman]

I wish hercules would show this in some form of dimensiontal display as well, but... that get's tricky after two dimensions :-)

[angerman]

@michaelpj after your experience with plutus. Do we have a sensible ci.nix <-> release.nix bridge? Can we make sure we build the same derivations on both somehow?

[hamishmack]

bors try

[iohk-bors]

try

Build succeeded

• buildkite/haskell-dot-nix
• ci/hydra:Cardano:haskell-nix:required

[michaelpj]

Yep, it's pretty easy. I'll make you a PR.