add merge ok to GHA workflow to simplify branch rules

Author: cognifloyd

.github/workflows/tox.yaml

@@ -47,3 +47,33 @@ jobs:
 
     - name: Test
       run: tox -e ${{ steps.tox-env.outputs.tox-env }}
+
+  set_merge_ok:
+    name: Set Merge OK
+    if: always() && !contains(needs.*.result, 'failure') && !contains(needs.*.result, 'cancelled')
+    needs:
+    - lint
+    - build
+    outputs:
+      merge_ok: ${{ steps.set_merge_ok.outputs.merge_ok }}
+    runs-on: ubuntu-latest
+    steps:
+    - id: set_merge_ok
+      run: echo 'merge_ok=true' >> ${GITHUB_OUTPUT}
+
+  merge_ok:
+    name: Merge OK
+    if: always()
+    needs:
+    - set_merge_ok
+    runs-on: ubuntu-latest
+    steps:
+    - run: |
+        merge_ok="${{ needs.set_merge_ok.outputs.merge_ok }}"
+        if [[ "${merge_ok}" == "true" ]]; then
+          echo "Merge OK"
+          exit 0
+        else
+          echo "Merge NOT OK"
+          exit 1
+        fi