Use 0 fetch depth

.github/workflows/public-api-check.yml

@@ -13,6 +13,7 @@ jobs:
       uses: actions/checkout@v2
       with:
         ref: ${{ github.event.pull_request.head.sha }}
+        # fetch-depth: 0
     - name: Set up Python
       uses: actions/setup-python@v2
       with: