title: Pytest coverage: run cov over multiple folders
body: <p>My project has a structure like:</p>
  
  <pre><code>root/
    .coveragerc
    folder_a/
    folder_b/
    tests/
      folder_a/
      folder_b/
  </code></pre>
  
  <p>I would like to run <code>coverage</code> against <code>folder_a</code> and <code>folder_b</code>. Is possible to run it in a single command? Something like <code>pytest --cov=* tests/ --cov-report html</code>...</p>