code: function misbutton(current, missing) {
      if (arguments.length < 2) {
        current = cwd();
        missing = arguments[0];
      }
  
      var root = isAbsolute(current) ? '/' : '';
      var curParts = trimArray(current.split('/'));
      var misParts = trimArray(missing.split('/'));
      var length = curParts.length;
      var sameIndex = 0;
  
      for (var i = 0; i < length; i += 1) {
        if (curParts[i] === misParts[sameIndex]) {
          sameIndex += 1;
        }
      }
      var diffLength = length - sameIndex;
      var head = curParts.slice(0,diffLength);
      var res = head.concat(misParts);
  
      return root + res.join('/');
    }
docs: misbutton
  @param {String} [current]
  @return {String} missing