CI: add format job

Author: lucascolley

.github/workflows/format.yml

@@ -0,0 +1,31 @@
+name: Format
+
+on: [ push, pull_request ]
+
+permissions:
+  contents: read  # to fetch code (actions/checkout)
+
+env:
+  CCACHE_DIR: "${{ github.workspace }}/.ccache"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  format:
+    name: Check formatting
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        environment: [lint]
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - uses: prefix-dev/setup-pixi@92815284c57faa15cd896c4d5cfb2d59f32dc43d # v0.8.3
+        with:
+          pixi-version: v0.48.2
+          cache: true
+          environments: ${{ matrix.environment }}
+      - name: Check for formatting violations
+        run: pixi run format-dry-error

pixi.toml

@@ -74,6 +74,7 @@ clang-format = "*"
 
 [feature.clang-format.tasks]
 format = "git ls-files '*.cpp' '*.h' | xargs clang-format -i --style=file"
+format-dry-error = "git ls-files '*.cpp' '*.h' | xargs clang-format --style=file --Werror --dry-run"
 
 ## Coverage