anchor.diff:      diffs.forEach(diff => {
         const filename = diffFilename(diff);
         const $filename = $(`#radio_${diff.id}`, review.page);
  -      diff.chunkIndex = 0
  -      diff.chunkCount = diff.lines.reduce((n,line) => n + (line.type === 'section'), 0);
  -      diff.hasBeenClicked = false;
         $filename.click(() => {
           selectLineCounts(filename);
           selectFilename($filename);
  
positive.code:     tip += '<span class="diff-line-count-icon same">=</span> number of deleted,added,unchanged lines.<br/>';
      tip += '<hr/>';
      tip += 'click a filename to review it.<br/>';
      tip += 'reclick a filename to cycle through its diffs.<br/>';
      tip += '<hr/>';
      tip += '<span class="diff-type-marker created"></span><span class="diff-filename created">created-file</span><br/>';
      tip += '<span class="diff-type-marker deleted"></span><span class="diff-filename deleted">deleted-file</span><br/>';
      tip += '<span class="diff-type-marker unchanged"></span><span class="diff-filename unchanged">unchanged-file</span><br/>';
      tip += '<span class="diff-type-marker renamed"></span><span class="diff-filename renamed">renamed-file</span>';
      tip += ' for old filename, hover over the <span class="diff-type-marker renamed"></span>';
      const $div = $('<div>', {
        class: 'diff-help-icon',
        'data-tip': tip
  
negative.code:   const makeDiffType = (diff) => {
      if (diff === '&nbsp;') { return diff; }
      const $div = $('<div>', { class:`diff-type-marker ${diff.type}` });
      let hoverTip = '';
      if (diff.type === 'renamed') {
        hoverTip += oldFilenameTip(diff);
      }
      if (diff.chunkCount > 0) {
        if (hoverTip != '') { hoverTip += '<br/>'; }
        hoverTip += chunkCountTip(diff);
      }
      if (hoverTip != '') {
        $div.attr('data-tip', hoverTip);
      }
      return outerHTML($div);
    };
  
    const oldFilenameTip = (diff) => {
      return `was<span class="diff-filename renamed">${diff.old_filename}</span>`;
    };
  
    const chunkCountTip = (diff) => {
      return `diff chunk count == ${diff.chunkCount}`;
    };
  
    // - - - - - - - - - - - - - - - - - - - - - - - -
  