Exit if no diff

.github/workflows/stubs.yaml

@@ -9,6 +9,7 @@ jobs:
       - uses: actions/checkout@v3
       - run: |
           bash generate_stubs.sh
+          git diff --exit-code --quiet && exit 0
           git config user.name github-actions
           git config user.email [email protected]
           git add *.pyi