private void updateTooltipText(@NlsSafe @Nullable String relativeSourceRootPath) {
    JComboBox<?> comboBox = getComboBox();
    if (relativeSourceRootPath != null && comboBox.getSelectedItem() == DirectoryChooser.ItemWrapper.NULL) {
      comboBox.setToolTipText(relativeSourceRootPath);
    }
    else {
      comboBox.setToolTipText(null);
    }
  }
private void updateTooltipText(@NlsSafe @Nullable String relativeSourceRootPath)