Abort if resulting pull would end up with no changes

.github/workflows/automerge.yml

@@ -9,6 +9,7 @@ permissions: write-all
 jobs:
   package_json:
     runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' || github.actor == 'renovate[bot]' }}
     steps:
     - uses: actions/[email protected]
       continue-on-error: true
@@ -26,7 +27,7 @@ jobs:
           git add package.json
           git -c user.name="GitHub" -c user.email="[email protected]" commit --author="github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>" -m"Fix package.json" | sed -n 1p || true
           git push
-          if [[ $(git status --porcelain | tee /dev/stderr | head -c1 | wc -c) -ne 0 || $(git clean -dffx | tee /dev/stderr | head -c1 | wc -c) -ne 0 ]]; then
+          if [[ $(git diff --stat $(git log -1 --skip=2 --format=%H) $(git log -1 --format=%H)) -eq 0 || $(git status --porcelain | tee /dev/stderr | head -c1 | wc -c) -ne 0 || $(git clean -dffx | tee /dev/stderr | head -c1 | wc -c) -ne 0 ]]; then
             exit 1
           fi
         fi