ci: check pr title

signed commit cannot be rebased onto main
so rebasing when merging PR has been disabled
in favor of the squash commit.
Thus we want the PR title to match the expected
format:
"[area]: [desc]"
and max 72 characters"

Signed-off-by: Cyril Fougeray <[email protected]>

.github/workflows/compliance.yml

@@ -1,33 +1,27 @@
-name: Format & Compliance
-on: [pull_request]
+name: Pull-Request Compliance
+on:
+  pull_request:
+    types: [opened, edited, reopened]
 
 jobs:
-  check-compliance:
-    name: Check formatting & commit message compliance
+  check-pr-title:
+    name: Check PR title
     runs-on: ubuntu-22.04
-    container:
-      image: ghcr.io/worldcoin/${{ vars.DOCKER_IMAGE_NAME }}:${{ vars.DOCKER_IMAGE_TAG }}
+    # See https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
+    env:
+      TITLE: ${{ github.event.pull_request.title }}
     steps:
-      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # pin@v3
-        with:
-          path: "${{ github.job }}/orb"
-      - name: Check formatting
+      - name: Check title format
         run: |
-          cd "${{ github.job }}/orb"
-          git config --global --add safe.directory /__w/open-orb-mcu-firmware/open-orb-mcu-firmware
-          pre-commit run --all-files --config utils/format/pre-commit-config.yaml
-      - name: Check commit message
-        run: |
-          cd "${{ github.job }}/orb"
-          # Un-shallow
-          git config remote.origin.fetch "+refs/heads/*:refs/remotes/origin/*"
-          # Deepen topic branch; checkout topic branch
-          git fetch origin ${{ github.event.pull_request.head.ref }} --depth=$(( ${{ github.event.pull_request.commits }} + 1 ))
-          git checkout ${{ github.event.pull_request.head.ref }}
-          # Fetch main for common origin
-          git fetch origin ${{ github.event.pull_request.base.ref }}:${{ github.event.pull_request.base.ref }} --depth=50
-          gitlint --config utils/format/.gitlint --commits ${{ github.event.pull_request.base.ref }}..
-      - name: Guide to contributing
-        if: failure()
-        run: |
-          echo "Take a look at CONTRIBUTING.md"
+          # has a colon which separates the area from the description
+          # max 72 characters
+          exit_code=0
+          if [[ ! ${TITLE} =~ ^[^:]+:.+$ ]]; then
+              echo "PR title must specify an area and a description, see README.md"
+              exit_code=1
+          fi
+          if [[ ${#TITLE} -gt 72 ]]; then
+              echo "PR title is too long, see README.md"
+              exit_code=1
+          fi
+          exit $exit_code