ci: check that PR titles follow Conventional Commits (#5143)

* ci: check that PR titles follow Conventional Commits

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

* ci: address Greptile review on the PR title check

Give the HLTB updater a Conventional Commits title so its PRs pass the
check, and strip line breaks from the title before echoing it so it
cannot start a workflow command.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 5.5 (1M context) <[email protected]>

.github/workflows/conventional-pr-title.yml

@@ -0,0 +1,41 @@
+name: Conventional PR Title
+
+# The PR title becomes the squash commit and the release notes line, so it
+# has to follow Conventional Commits: `type(scope)!: description`.
+
+on:
+  pull_request:
+    types: [opened, edited, synchronize, reopened]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+permissions: {}
+
+jobs:
+  check-title:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - name: Check the PR title
+        env:
+          # Read from env, never interpolated into the script, since the title is untrusted.
+          PR_TITLE: ${{ github.event.pull_request.title }}
+        run: |
+          types="feat|fix|perf|refactor|revert|docs|style|test|build|ci|chore"
+          pattern="^(${types})(\([a-z0-9][a-z0-9._/, -]*\))?!?: [^ ].*$"
+
+          if [[ "$PR_TITLE" =~ $pattern ]]; then
+            echo "PR title follows Conventional Commits."
+            exit 0
+          fi
+
+          echo "::error::PR title must follow Conventional Commits: type(scope)!: description"
+          # Line breaks would let the title start a workflow command line.
+          echo "Got: ${PR_TITLE//[$'\r\n']/ }"
+          echo "Allowed types: ${types//|/, }"
+          echo "Examples:"
+          echo "  feat(saves): favorite and label saves and states"
+          echo "  fix: serialize single-file ROM promotion across gunicorn workers"
+          exit 1

.github/workflows/update-hltb-api-url.yml

@@ -40,10 +40,10 @@ jobs:
         with:
           add-paths: |
             backend/handler/metadata/fixtures/hltb_api_url
-          commit-message: "Update HLTB API URL [skip CI]"
+          commit-message: "chore(hltb): update HLTB API URL [skip CI]"
           branch: update-hltb-api-url
           sign-commits: true
-          title: "Update HLTB API URL [skip CI]"
+          title: "chore(hltb): update HLTB API URL [skip CI]"
           reviewers: |
             gantoine
 

CONTRIBUTING.md

@@ -57,6 +57,7 @@ If you would like to translate the project into another language, create a new f
 - Update the documentation if necessary.
 - Ensure all existing tests pass, and add new tests for new functionality.
 - Use clear and descriptive titles and descriptions for your pull requests.
+- Write the PR title as a [Conventional Commit](https://www.conventionalcommits.org/), such as `fix(scan): keep partial bytes out of the fallback hash`. Allowed types are `feat`, `fix`, `perf`, `refactor`, `revert`, `docs`, `style`, `test`, `build`, `ci` and `chore`, and CI checks the title.
 
 ## Code Style