title: dynamically creating output folder based on timestamp
body: <p>I used to use a <strong>runner.py</strong> with my pytest framework in order to get around the bug with combining markers and string params, e.g.:</p>
  
  <pre><code>-k 'foo' -m 'bar'
  </code></pre>
  
  <p>I also used the runner to get the test run's starting timestamp and create an output folder output// to which I write my logs and the html report, save any screenshots, etc.</p>
  
  <p>runner.py excerpt:</p>
  
  <pre><code>    timestamp = time.strftime('%y%m%d-%H%M%S')
      # the following are used by conftest.py
      output_path = utils.generate_output_path(timestamp) 
      folder = utils.create_output_folder(output_path)
  
      def main():
          args = sys.argv[1:]
          args.append('-v')
          args.append('--timestamp=%s' % timestamp)
          args.append('--output_target=%s' % folder)
          args.append('--html=%s/results.html' % folder)
          pytest.main(args, plugins=plgns)
  
      if __name__ == "__main__":
          main()
  </code></pre>
  
  <p>I want to lose the runner.py and use straight CLI args and fixtures/hooks but not manually pass in timestamp, output_target, or the html report path, but have so far been unable find a way to change that config, for example by modifying config.args.</p>
  
  <p>How can I dynamically write timestamp, output_target, and the html path so that pytest uses them during initialization?</p>