fix: ff?

.github/workflows/main.yml

@@ -268,6 +268,7 @@ jobs:
           echo "Current branch is: ${{ github.head_ref }}"
           echo "Current branch is: ${{ github.base_ref }}"
           echo "Current branch is: ${{ github.event_name }}"
+          git config pull.ff only       # fast-forward only
           git pull origin ${{ github.head_ref }}
 
       - name: Set up Python ${{ matrix.python-version }}