ci: use Nix on CI

Keep Docker as a sanity check

.github/workflows/ci.yml

@@ -16,73 +16,63 @@ defaults:
 
 jobs:
 
-  build:
-    timeout-minutes: 10
-    name: "Build: compile source code and export HTML"
+  nix:
     runs-on: ubuntu-latest
+    name: "Build using Nix"
     steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
       -
-        name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v1
-      -
-        name: Checkout
-        uses: actions/checkout@v2
-      - # This is very wasteful but caching docker images on GH actions is
-        # INSANELY DIFFICULT!!! Honestly they bring it on themselves, this is
-        # not an abstruse setup. But until I can cache docker images (let alone
-        # layers), without pollution between branches / PRs, and without
-        # 1873907182301273 lines of code, config and separate auths and external
-        # services, I’ll just stick to rebuilding the entire image every time.
-        name: Build the Docker image
-        run: docker-compose build
+        name: Install Nix
+        uses: cachix/install-nix-action@v20
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
       -
         name: Tangle code and export HTML
-        run: docker-compose run --rm build
+        run: "nix build .#dist"
+      -
+        name: Test
+        run: nix flake check
       -
         name: Create artifact bundle
-        run: tar cvf artifacts.tar test tomono index.html style.css
+        run:
+          (cd result/bin && tar cvf $OLDPWD/artifacts.tar tomono)
+          (cd result/doc && tar rvf $OLDPWD/artifacts.tar index.html style.css)
       -
         uses: actions/upload-artifact@v3
         with:
           name: bundle-${{github.sha}}
           path: artifacts.tar
 
-  test:
+  docker:
     timeout-minutes: 10
-    name: "Test"
-    strategy:
-      matrix:
-        os: [windows-latest, ubuntu-latest]
-    runs-on: ${{ matrix.os }}
-    needs: build
+    name: "Build using Docker"
+    runs-on: ubuntu-latest
     steps:
       -
-        name: Remove files before artifact download
-        run: rm -rf artifacts.tar
-      -
-        uses: actions/download-artifact@v3
-        with:
-          name: bundle-${{github.sha}}
-      -
-        name: Unpack artifacts
-        run: tar xvf artifacts.tar
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
       -
-        name: Set up git for CI
-        run: |
-          git config --global user.name CI
-          git config --global user.email c@i
-          git config --global init.defaultBranch master
-          git config --global core.autocrlf input
+        name: Checkout
+        uses: actions/checkout@v2
+      - # This is very wasteful but caching docker images on GH actions is
+        # INSANELY DIFFICULT!!! Honestly they bring it on themselves, this is
+        # not an abstruse setup. But until I can cache docker images (let alone
+        # layers), without pollution between branches / PRs, and without
+        # 1873907182301273 lines of code, config and separate auths and external
+        # services, I’ll just stick to rebuilding the entire image every time.
+        name: Build the Docker image
+        run: docker compose build
       -
-        name: Run tests
-        run: ./test
+        name: Tangle code and export HTML
+        run: docker compose run --rm build
 
   deploy_pages:
     timeout-minutes: 10
     if: ${{ github.ref_type == 'branch' && github.ref == 'refs/heads/master' }}
     name: "Deploy the HTML to GitHub Pages"
     runs-on: ubuntu-latest
-    needs: build
+    needs: nix
     steps:
       -
         name: Checkout