.github: Add lint workflow

.github/workflows/lint.yml

@@ -0,0 +1,44 @@
+name: Lint
+
+on:
+  pull_request:
+  push:
+jobs:
+  lint:
+    name: Lint
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4.1.1
+
+      - uses: DeterminateSystems/nix-installer-action@v9
+        continue-on-error: true # Self-hosted runners already have Nix installed
+
+      - name: Install Attic
+        run: |
+          if ! command -v attic &> /dev/null; then
+            ./.github/install-attic-ci.sh
+          fi
+
+      - name: Configure Attic
+        run: |
+          : "${ATTIC_SERVER:=https://staging.attic.rs/}"
+          : "${ATTIC_CACHE:=attic-ci}"
+          echo ATTIC_CACHE=$ATTIC_CACHE >>$GITHUB_ENV
+          export PATH=$HOME/.nix-profile/bin:$PATH # FIXME
+          attic login --set-default ci "$ATTIC_SERVER" "$ATTIC_TOKEN"
+          attic use "$ATTIC_CACHE"
+        env:
+          ATTIC_SERVER: ${{ secrets.ATTIC_SERVER }}
+          ATTIC_CACHE: ${{ secrets.ATTIC_CACHE }}
+          ATTIC_TOKEN: ${{ secrets.ATTIC_TOKEN }}
+
+      - name: Cache dev shell
+        run: |
+          .ci/cache-shell.sh
+          system=$(nix-instantiate --eval -E 'builtins.currentSystem')
+          echo system=$system >>$GITHUB_ENV
+
+      - name: Check rustfmt
+        run: .ci/run just ci-rustfmt

justfile

@@ -41,3 +41,7 @@ ci-unit-tests matrix:
 	system=$(nix-instantiate --eval -E 'builtins.currentSystem')
 	tests=$(nix build .#internalMatrix."$system".\"{{ matrix }}\".attic-tests --no-link --print-out-paths -L)
 	find "$tests/bin" -exec {} \;
+
+# (CI) Run rustfmt check
+ci-rustfmt:
+	cargo fmt --check