anchor.diff:  
     // - - - - - - - - - - - - - - - - - - - - - - - -
   
  -  var makeDiffFilenamesColumn = function(diffs) {
  -    var html = '';
  +  const makeDiffFilenamesColumn = (diffs) => {
  +    let html = '';
       html += '<table>';
  -    $.each(sortedDiffs(diffs), function(_, diff) {
  -      var td = $('<td>');
  -      var filenameDiv =
  +    $.each(sortedDiffs(diffs), (_, diff) => {
  +      const td = $('<td>');
  +      const filenameDiv =
           $('<div>', {
               'class': 'filename',
               'data-filename': diff.filename,
  
positive.code: 
    // - - - - - - - - - - - - - - - - - - - - - - - -
  
    var showLatestNoDiff = function() {
      var lastTag = -1;
      param.wasTag = lastTag;
      param.nowTag = lastTag;
      refresh();
  
negative.code:   // refresh [fork] {create a new practice-session}
    //-----------------------------------------
  
    const refreshForkButton = () => {
      const button = $('#fork-button');
      cd.setTip(button, () => {
        const tip = 'setup a new session from ' + param.avatar + ' ' + param.nowTag;
        cd.showHoverTip(button, tip);
      });
    };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
  
    const doFork = () => {
      const forkParams = {
            id: param.id,
        avatar: param.avatar,
           tag: param.nowTag
      };
      $.getJSON('/forker/fork', forkParams, function(data) {
        if (data.forked) {
          cd.newDojoDialog(data);
        } else {
  