added checkout

Author: Petr Sramek

.github/workflows/format-cs-files.yml

@@ -39,7 +39,7 @@ jobs:
       run: dotnet tool install -g dotnet-format
     - name: Format with .NET ${{ vars.DOTNET_SDK_VERSION }}
       run: |
-        git pull origin ${{ github.head_ref || github.ref }}
+        git checkout origin ${{ github.head_ref || github.ref }}
         dotnet format whitespace --verbosity diagnostic
         dotnet format style --verbosity diagnostic
         dotnet format analyzers --diagnostics IDE0073 --verbosity diagnostic