ci: update checkout action configuration in ci workflow

- add 'ref' parameter to the checkout action
- set 'ref' to use either the head ref for pull requests or the ref name for other events

Author: johelder

.github/workflows/ci.yml

@@ -57,6 +57,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          ref: ${{ github.head_ref || github.ref_name }}
 
       - name: Setup
         uses: ./.github/actions/setup