ci: checkout the actual ref instead of github's merge commit

Author: onerandomusername

.github/workflows/lint_test.yml

@@ -46,6 +46,10 @@ jobs:
       # Checks out the repository in the current folder.
       - name: Checks out repository
         uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
+          ref: ${{ github.head_ref }}
+
 
       # Set up the right version of Python
       - name: Set up Python ${{ env.PYTHON_VERSION }}