code: function _openPath(treeData, path) {
          var objectPath = _filePathToObjectPath(treeData, path);
  
          function setOpen(node) {
              return node.set("open", true);
          }
  
          while (objectPath && objectPath.length) {
              var node = treeData.getIn(objectPath);
              if (isFile(node)) {
                  objectPath.pop();
              } else {
                  if (!node.get("open")) {
                      treeData = treeData.updateIn(objectPath, setOpen);
                  }
                  objectPath.pop();
                  if (objectPath.length) {
                      objectPath.pop();
                  }
              }
          }
  
          return treeData;
      }
docs: @private
  
  Opens the directories along the provided path.
  
  @param {Immutable.Map} treeData
  @param {string} path Path to open