anchor.diff:              scrollTop: '+=' + (section.offset().top - 250) + 'px'
             }, halfSecond);
             sectionIndex += 1;
  -          sectionIndex %= sectionCount;
  +          sectionIndex %= diff.section_count;
           }
           param.filename = filename;
           alreadyOpened.push(filename);
  
positive.code: 
    // - - - - - - - - - - - - - - - - - - - - - - - -
    const buildDiffFilenameHandlers = (diffs) => {
      // Builds click handlers for all filenames for a given
      // [ kata-id, was-index, now-index] tuple.
      const reClicked = (filename) => param.filename === filename;
      const alreadyOpened = [];
  
      const loadFrom = (diff) => {
        const filename = diffFilename(diff);
        const sectionCount = diff.section_count;
        let sectionIndex = 0;
  
        return () => {
          // select line-counts
          $('.diff-line-count').attr('disabled', true);
  
negative.code: 
          // when reclicking a filename then scroll to next diff-chunk.
          // But not when returning to a previously scrolled file.
          if (diff.section_count > 0 && (reClicked(filename) || !alreadyOpened.includes(filename))) {
            const $diffSheet = $(`[id="diff_file_content_for_${filename}"]`);
            const section = $(`#${diff.id}_section_${sectionIndex}`);
            const halfSecond = 500;
  