Move clang-format checks to pre-commit

.github/workflows/checks.yml

@@ -9,8 +9,21 @@ on:
 jobs:
   format:
     runs-on: ubuntu-latest
-    container: ghcr.io/acts-project/format10:v11
+    env:
+      PRE_COMMIT_HOME: '/tmp/pre-commit'
+
     steps:
-      - uses: actions/checkout@v3
-      - name: Check
-        run: .github/check_format.sh .
+      - name: Checkout
+        uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ${{ env.PRE_COMMIT_HOME }}
+          key: ${{ runner.os }}-${{ hashFiles('.pre-commit-config.yaml') }}
+      - name: Install pre-commit
+        run: pip install pre-commit
+      - name: Run pre-commit
+        run: pre-commit run --all-files --show-diff-on-failure

.pre-commit-config.yaml

@@ -0,0 +1,7 @@
+repos:
+  - repo: https://github.com/pre-commit/mirrors-clang-format
+    rev: v10.0.1
+    hooks:
+      - id: clang-format
+        types_or: [file]
+        files: \.(cpp|hpp|ipp|cu|cuh|sycl|hip)$

README.md

@@ -324,6 +324,25 @@ Attaching file performance_track_finding.root as _file0...
 root [1] finding_trackeff_vs_eta->Draw()
 ```
 
+## Contributing
+
+### Code formatting
+
+The traccc code is formatted using clang-format; the recommended way to ensure that your code is properly formatted is to use [pre-commit](https://pre-commit.com/). The pre-commit webpage has a useful guide for using the tool, but the simplest way of using it (without installing it as a pre-commit hook) is as follows. First, install the tool with your favourite Python package manager:
+
+```console
+# With pip
+$ pip install pre-commit
+# With pipx
+$ pip install pre-commit
+```
+
+The install step needs to be executed only once. After that, the code can be easily formatted as follows:
+
+```console
+$ pre-commit run --all-files
+```
+
 ## Continuous benchmark
 
 Monitoring the event throughput of track reconstruction with the toy geometry