add checkout ref

.github/workflows/cypress.yml

@@ -18,6 +18,9 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.pull_request.head.ref }}
+          fetch-depth: 0
       - name: Derive appropriate SHAs for base and head for `nx affected` commands
         uses: nrwl/nx-set-shas@v2
       - name: Use Node.js 16