add CI step to print baselines

Author: gabritto

.github/workflows/ci.yml

@@ -81,6 +81,13 @@ jobs:
       - run: git add .
       - run: git diff --staged --exit-code --stat
 
+      - name: Print baseline diff on failure
+        if: ${{ failure() && steps.test.conclusion == 'failure' }}
+        run: |
+          npx hereby baseline-accept
+          git add testdata/baselines/reference
+          git diff --staged --exit-code
+
   lint:
     runs-on: ubuntu-latest
     steps: