ci: validate pull request titles

Author: danielroe

.github/workflows/semantic-pull-requests.yml

@@ -0,0 +1,35 @@
+name: chore
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+      - synchronize
+
+permissions: {}
+
+jobs:
+  semantic-pr:
+    permissions:
+      contents: read
+      pull-requests: read # for amannn/action-semantic-pull-request to analyze PRs
+      statuses: write # for amannn/action-semantic-pull-request to mark status of analyzed PR
+    if: github.repository == 'npmx-dev/npmx.dev'
+    runs-on: ubuntu-latest
+    name: semantic-pr
+    steps:
+      - name: Validate PR title
+        uses: amannn/action-semantic-pull-request@48f256284bd46cdaab1048c3721360e808335d50 # v6.1.1
+        with:
+          scopes: |
+            docs
+            i18n
+            deps
+          subjectPattern: ^(?![A-Z]).+$
+          subjectPatternError: |
+            The subject "{subject}" found in the pull request title "{title}"
+            didn't match the configured pattern. Please ensure that the subject
+            doesn't start with an uppercase character.
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

CONTRIBUTING.md

@@ -365,13 +365,27 @@ Make sure to read about [Playwright best practices](https://playwright.dev/docs/
 4. ensure CI checks pass (lint, type check, tests)
 5. request review from maintainers
 
-### Commit messages
+### Commit messages and PR titles
 
-Write clear, concise commit messages that explain the "why" behind changes:
+Write clear, concise PR titles that explain the "why" behind changes.
+
+We use [Conventional Commits](https://www.conventionalcommits.org/). Since we squash on merge, the PR title becomes the commit message in `main`, so it's important to get it right.
+
+Format: `type(scope): description`
+
+**Types:** `feat`, `fix`, `docs`, `style`, `refactor`, `perf`, `test`, `build`, `ci`, `chore`, `revert`
+
+**Scopes (optional):** `docs`, `i18n`, `deps`
+
+**Examples:**
 
 - `fix: resolve search pagination issue`
 - `feat: add package version comparison`
-- `docs: update installation instructions`
+- `fix(i18n): update French translations`
+- `chore(deps): update vite to v6`
+
+> [!NOTE]
+> The subject must start with a lowercase letter. Individual commit messages within your PR don't need to follow this format since they'll be squashed.
 
 ## Pre-commit hooks
 

package.json

@@ -99,7 +99,7 @@
     "*.{js,ts,mjs,cjs,vue}": [
       "vite lint --fix"
     ],
-    "*.{js,ts,mjs,cjs,vue,json,md,html,css}": [
+    "*.{js,ts,mjs,cjs,vue,json,yml,md,html,css}": [
       "vite fmt"
     ]
   },