The configuration must be inside a 'with:'

.github/workflows/python-app.yml

@@ -16,7 +16,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-      fetch-depth: 0
+      with:
+        fetch-depth: 0
     - name: Set up Python 3.7
       uses: actions/setup-python@v2
       with: