document path bias torrc options in the code

  /**
   * Parameters for path-bias detection.
   * @{
   */
  int PathBiasCircThreshold;
  double PathBiasNoticeRate;
  double PathBiasDisableRate;
  int PathBiasScaleThreshold;
  int PathBiasScaleFactor;
  /** @} */

What are each of these? How do they differ? Is DisableRate the one about dropping guards? This doxygen comment doesn't help me.