code: function resolveInRoot(root) {
      var input, result, err;
  
      input = _.chain(arguments)
          .toArray()
          .slice(1)
          .reduce(function(current, p) {
              // Handle path relative to book root ("/README.md")
              if (p[0] == "/" || p[0] == "\\") return p.slice(1);
  
              return current? path.join(current, p) : path.normalize(p);
          }, "")
          .value();
  
      result = path.resolve(root, input);
  
      if (!isInRoot(root, result)) {
          err = new Error("EACCESS: \"" + result + "\" not in \"" + root + "\"");
          err.code = "EACCESS";
          throw err;
      }
  
      return result;
  }
docs: Resolve paths in a specific folder Throw error if file is outside this folder