function mergeWithRoot(heap, node) {
  if (!heap.root) {
    heap.root = node;
  }
  else {
    node.right = heap.root.right;
    node.left = heap.root;
    heap.root.right.left = node;
    heap.root.right = node;
  }
}
Function used to merge the given node with the root list.

@param {FibonacciHeap} heap - Target heap.
@param {Node}          node - Target node.