gitlab-ci: Bump docker image

Bizarrely, the nixos/nix:2.3 tag still pointed to an image that is over two years old, while nixos/nix:2.3.13 is much newer. Use the latter.

Fixes #35 (closed), where the nixos image was too old to include the new Let's Encrypt certificate.

changed the description

enabled an automatic merge when the pipeline for 59ed0c65 succeeds

It's a bit disheartening that a NixOS-based CI setup can bitrot like this, but luckily the fix looks simple. I don't know if we'll know for sure if it works until after merging this, given that the problem resides in the update-repo job (which, AFAICT, isn't run on MRs). In that case, the most prudent course of actions seems to be just landing this and seeing what happens.

approved this merge request

Oops, there are some build failures here that are not your fault:

• singletons is failing since it is listed in https://gitlab.haskell.org/ghc/head.hackage/-/blob/4625538ce31fae28b4ac1f57ef5d53db6edd13a4/ci/config.sh#L102 without a version constraint.
• OneTuple is failing on HEAD due to ghc#20562 (closed). It would be simple enough to patch around this.
• inj-base et al. are failing on HEAD due to ghc#20584 (closed). There is a fix in flight in ghc!6866 (merged), but until that lands, we can just mark these libraries as expected to fail on HEAD.

I'll push fixes later today.

aborted the automatic merge because source branch was updated

added 3 commits

• 1d95e239 - ci/config.sh: Constraint all extra_packages with patches
• 3bbe1d2b - Mark some libraries as expected HEAD failures due to ghc#20584 (closed)
• 460c708d - Patch OneTuple to work around ghc#20562 (closed) on HEAD

Compare with previous version

enabled an automatic merge when the pipeline for 460c708d succeeds

merged

mentioned in commit 911d481b

I've confirmed that the CI on the master branch is fully functional once more. Thanks again, @bgamari!