Add PR/Push specific commit message handling in CI

* The previous ignoring of the top commit was to avoid badly-written merge
  commits added by github, we want to continue doing that for PRs but check all
  commits on push as a safety measure.

.github/workflows/ci.yml

@@ -23,7 +23,19 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 100
-    - name: Check commit messages
+    - name: Check commit messages (PR)
+      if: ${{ github.event_name == 'pull_request' }}
+      run: |
+        if git log --oneline | tail -n +2 | head -n 100 | grep -v 76f9176 | cut -d ' ' -f2- | grep -q '.\{73\}'; then
+          (echo -n "::error::";
+           echo "Some commit message summary lines are too long. See CONTRIBUTING.md for more information.";
+           echo "Invalid commits:";
+           echo;
+           git log --oneline | tail -n +2 | head -n 100 | grep -v 76f9176 | cut -d ' ' -f2- | grep '.\{73\}';) | tr '\n' '\001' | sed -e 's#\x01#%0A#g';
+          exit 1;
+        fi
+    - name: Check commit messages (Push)
+      if: ${{ github.event_name == 'push' }}
       run: |
         if git log --oneline | head -n 100 | grep -v 76f9176 | cut -d ' ' -f2- | grep -q '.\{73\}'; then
           (echo -n "::error::";