Fetch github.ref in the checkout action

Author: adamziel

.github/workflows/has-valid-blueprint-json.yml

@@ -10,6 +10,9 @@ jobs:
         steps:
             - name: Checkout code
               uses: actions/checkout@v2
+              with:
+                ref: ${{ github.ref }}
+                fetch-depth: 0
 
             - name: Fetch trunk
               run: |