REMOVEME

Author: Ocramius

.github/workflows/mutation-tests.yml

@@ -27,7 +27,7 @@ jobs:
       - name: "Checkout $GITHUB_BASE_REF branch (for diffing)"
         uses: "actions/checkout@v2"
         with:
-          ref: ${{ env.GITHUB_BASE_REF }}
+          ref: 1.9.x
 
       - name: "Checkout"
         uses: "actions/checkout@v2"