GitHub Actions actions/checkout@v1 checked out code as a detached HEAD,
which caused Code Climate test coverage reports to appear as on the HEAD branch.
Coverage reports should now appear on an upstream branch.
From the actions/checkout@v2 release notes: https://github.com/actions/checkout/blob/v2/README.md
> - Creates a local branch
> - No longer detached HEAD when checking out a branch
> - A local branch is created with the corresponding upstream branch set
