Add a new CI step to detect raw issue references

Issue references shall now be used with the Rust GCC prefix in order to
avoid mixing gccrs issues and GCC bugzilla PRs.

ChangeLog:

	* .github/workflows/commit-format.yml: Add a new step to detect issue
	references in commit messages.

Signed-off-by: Pierre-Emmanuel Patry <[email protected]>

.github/workflows/commit-format.yml

@@ -108,3 +108,33 @@ jobs:
           done < <(git rev-list --reverse "$rev_list" )
 
           exit $retval;
+
+  check-issue-reference:
+    runs-on: ubuntu-latest
+    continue-on-error: true # We do not want to block merge if it is a legitimate GCC bugzilla reference.
+    name: check-issue-reference
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+
+      - name: Check for issue number reference in commit messages
+        run: |
+          retval=0;
+          rev_list="origin/${{ github.event.pull_request.base.ref }}..${{ github.event.pull_request.head.sha }}"
+          for commit in $(git rev-list --reverse "$rev_list"); do
+            if [ "$(git log --format=%B -n 1 \"$commit\" | grep '#[0-9]*' | grep -v -i 'Rust-GCC/gccrs#[0-9]*' | wc -l)" -ne 0 ]; then
+              echo "$commit: KO"
+              retval=1
+            else
+              echo "$commit: OK"
+            fi
+          done;
+          if [ "$retval" -ne 0 ]; then
+            echo "Some raw issue references were found (eg. #4242)."
+            echo "You shall rewrite the faulty commit message with this format: Rust-GCC/gccrs#4242"
+            echo "You may ignore this CI step if it represents a valid GCC bugzilla or external repository reference instead."
+          fi
+          exit $retval;