fixup! ci: prevent accidental merge of fixup! commits

.github/workflows/ci.yml

@@ -14,6 +14,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.ref }}
       - name: Check for fixup! commits
         run: |
           git fetch origin