fix(ci): check out with ref to allow auto-commits

Author: metacosm

.github/workflows/pr.yml

@@ -11,6 +11,8 @@ jobs:
         kubernetes: ['v1.17.13','v1.18.12','v1.19.4']
     steps:
       - uses: actions/checkout@v2
+        with:
+          ref: ${{ github.head_ref }} // to avoid cloning in detached state (which would break committing)
       - name: Format code
         uses: axel-op/googlejavaformat-action@v3
         with: