adds building oci containers #4

	# https://github.com/marketplace/actions/install-nix

	# Builds oci container in a rather convoluted way.

	name: "ci-oci"
	on:
	pull_request:
	push:

	concurrency:
	group: ${{ github.ref }}
	cancel-in-progress: true

	jobs:
	tests:
	runs-on: ubuntu-latest
	steps:

	- uses: actions/checkout@v4

	- name: Install nix
	uses: cachix/install-nix-action@v27

	# https://github.com/marketplace/actions/cache-nix-store
	- name: Restore and cache Nix store
	uses: nix-community/cache-nix-action@v5
	with:
	# restore and save a cache using this key
	# TODO: Also hash the cabal.config and *cabal files, since we depend on them
	primary-key: nix-${{ runner.os }}-${{ hashFiles('*/.nix') }}
	# if there's no cache hit, restore a cache by this prefix
	restore-prefixes-first-match: nix-${{ runner.os }}-
	# collect garbage until Nix store size (in bytes) is at most this number
	# before trying to save a new cache
	gc-max-store-size-linux: 1073741824
	# do purge caches
	purge: true
	# purge all versions of the cache
	purge-prefixes: cache-${{ runner.os }}-
	# created more than this number of seconds ago relative to the start of the `Post Restore` phase
	purge-created: 0
	# except the version with the `primary-key`, if it exists
	purge-primary-key: never

	- run: nix build --accept-flake-config .#containers.x86_64-linux.wst.copyTo
	- run: ./result/bin/copy-to oci-archive:oci.tar
	- run: ls -alh oci.tar

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