Add commitlint configuration and compliance checks

.commitlintrc.json

@@ -0,0 +1,40 @@
+{
+  "extends": [
+    "@commitlint/config-conventional"
+  ],
+  "rules": {
+    "type-enum": [
+      2,
+      "always",
+      [
+        "build",
+        "chore",
+        "ci",
+        "docs",
+        "feat",
+        "fix",
+        "perf",
+        "refactor",
+        "revert",
+        "security",
+        "style",
+        "test"
+      ]
+    ],
+    "subject-case": [
+      2,
+      "always",
+      [
+        "sentence-case",
+        "start-case",
+        "pascal-case",
+        "upper-case"
+      ]
+    ],
+    "header-max-length": [
+      2,
+      "always",
+      120
+    ]
+  }
+}

.github/workflows/compliance.yaml

@@ -0,0 +1,57 @@
+# SPDX-FileCopyrightText: 2026 Institute for Automation of Complex Power Systems, RWTH Aachen University
+# SPDX-License-Identifier: Apache-2.0
+
+name: Compliance checks
+
+on:
+    pull_request:
+        branches: [master, main]
+
+permissions:
+    contents: read
+
+jobs:
+    conventional-commits:
+        name: Conventional commit messages
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v7
+              with:
+                  fetch-depth: 0
+
+            - uses: actions/setup-node@v5
+              with:
+                  node-version: "20"
+
+            - name: Install commitlint
+              run: npm install --no-save @commitlint/cli @commitlint/config-conventional
+
+            # The merge commit takes the PR title, so that is what Release Please reads.
+            - name: Fail if the pull request title is not a conventional commit
+              env:
+                  PR_TITLE: ${{ github.event.pull_request.title }}
+              run: |
+                  if ! printf '%s\n' "$PR_TITLE" | npx commitlint --verbose; then
+                    echo ""
+                    echo "The pull request title becomes the merge commit subject on master."
+                    echo "Use a conventional commit subject, for example:"
+                    echo ""
+                    echo "  fix: Coding style"
+                    echo ""
+                    exit 1
+                  fi
+
+            - name: Fail if a commit in this branch is not a conventional commit
+              run: |
+                  BASE=${{ github.event.pull_request.base.sha }}
+                  HEAD=${{ github.event.pull_request.head.sha }}
+                  if ! npx commitlint --from "$BASE" --to "$HEAD" --verbose; then
+                    echo ""
+                    echo "Rewrite the offending commit messages, then force-push:"
+                    echo ""
+                    echo "  git rebase -i $BASE"
+                    echo "  git push --force-with-lease"
+                    echo ""
+                    echo "Or install the pre-commit hooks (see CONTRIBUTING.md) to catch this locally."
+                    exit 1
+                  fi

.pre-commit-config.yaml

@@ -3,6 +3,10 @@
 
 # See https://pre-commit.com for more information
 # See https://pre-commit.com/hooks.html for more hooks
+
+# commitlint runs at commit-msg, so plain `pre-commit install` must wire that stage too.
+default_install_hook_types: [pre-commit, commit-msg]
+
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v5.0.0
@@ -73,6 +77,13 @@ repos:
     hooks:
       - id: reuse-lint-file
 
+  - repo: https://github.com/alessandrojcm/commitlint-pre-commit-hook
+    rev: "v9.26.0"
+    hooks:
+      - id: commitlint
+        stages: [commit-msg]
+        additional_dependencies: ["@commitlint/config-conventional@19.8.1"]
+
   - repo: local
     hooks:
       - id: dco-hook