code: public TreeBuilder<T> subTree(Path path, Tree<T> subtree, boolean fullPath) {
          treeStack.add(new SubPathTree<T>(subtree, path, fullPath));
          return this;
      }
docs: Add a tree responsible for a subpath of the base tree.
  
  @param path     sub path to handle
  @param subtree  tree to delegate to for the path
  @param fullPath if true, send resources to the subtree with the original full path, otherwise store with a path
  relative to the path
  
  @return builder