Add commitlint workflow for testing

.github/workflows/.commitlintrc.cjs

@@ -0,0 +1,38 @@
+// Parse UHD's area-prefixed subjects and apply repository message limits.
+module.exports = {
+  parserPreset: {
+    parserOpts: {
+      headerPattern: /^(\S(?:.*\S)?): (\S(?:.*\S)?)$/,
+      headerCorrespondence: ['scope', 'subject'],
+    },
+  },
+  plugins: [
+    {
+      rules: {
+        'header-ideal-length': (parsed, when, value) => {
+          const isValid = parsed.header.length <= value;
+          return [
+            when === 'never' ? !isValid : isValid,
+            `header should be ${value} characters or fewer`,
+          ];
+        },
+        'no-fixup-commit': (parsed) => [
+          !/^fixup!\s/i.test(parsed.header)
+            && !/:\s*fixup!\s/i.test(parsed.header),
+          'fixup commits are not allowed',
+        ],
+      },
+    },
+  ],
+  defaultIgnores: false,
+  rules: {
+    'scope-empty': [2, 'never'],
+    'subject-empty': [2, 'never'],
+    'header-ideal-length': [1, 'always', 50],
+    'header-max-length': [2, 'always', 72],
+    'body-empty': [2, 'never'],
+    'body-leading-blank': [2, 'always'],
+    'body-max-line-length': [2, 'always', 72],
+    'no-fixup-commit': [2, 'always'],
+  },
+};

.github/workflows/commitlint.yml

@@ -0,0 +1,56 @@
+name: Commit Message Lint
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+
+permissions:
+  contents: read
+
+jobs:
+  commitlint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out pull request head
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+
+      - name: Lint pull request commits
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          set -o pipefail
+          printf '## Commit message lint\n\n' >> "$GITHUB_STEP_SUMMARY"
+          output_file="$(mktemp)"
+          trap 'rm -f "$output_file"' EXIT
+          # Lint only commits introduced by this pull request.
+          if npx --yes --package @commitlint/cli@19.8.1 -- commitlint \
+            --config .github/workflows/.commitlintrc.cjs \
+            --from="$BASE_SHA" \
+            --to="$HEAD_SHA" 2>&1 | tee "$output_file"; then
+            if [[ -s "$output_file" ]]; then
+              printf 'Commit message lint passed with warnings.\n\n' \
+                >> "$GITHUB_STEP_SUMMARY"
+              while IFS= read -r line; do
+                printf '    %s\n' "$line" >> "$GITHUB_STEP_SUMMARY"
+              done < "$output_file"
+            else
+              printf 'All pull request commit messages passed.\n' \
+                >> "$GITHUB_STEP_SUMMARY"
+            fi
+          else
+            printf 'Commit message lint failed.\n\n' >> "$GITHUB_STEP_SUMMARY"
+            while IFS= read -r line; do
+              printf '    %s\n' "$line" >> "$GITHUB_STEP_SUMMARY"
+            done < "$output_file"
+            exit 1
+          fi