anchor.diff:    tabs.reserves = filename => {
       const tabNames = [];
       tabNames.push(tabs.output().text());
  -    tabNames.push('status');
       tabNames.push(tabs.repl().text());
       return tabNames.includes(filename);
     };
  
positive.code: 
  <div class="tab-filenames">
    <div class="tab output">output</div>
    <div class="tab filename">cyber-dojo.sh</div>
    <div class="tab REPL">+REPL</div>
  </div>
  
  
negative.code:     // Alt-O tabs hot-key navigation
      // See app/assets/javascripts/cyber-dojo_codemirror.js
      // See app/views/shared/_hotkeys.html.erb
      const text = tabs.selected().text();
      if (text === 'output') {
        tabs.filename().click();
      } else {
        tabs.output().click();
      }
    };
  
  