code: public void merge(ChangesItem changesItem)
     {
        workspaceChangedSize += changesItem.getWorkspaceChangedSize();
  
        for (Entry<String, Long> changesEntry : changesItem.calculatedChangedNodesSize.entrySet())
        {
           String nodePath = changesEntry.getKey();
           Long currentDelta = changesEntry.getValue();
  
           Long oldDelta = calculatedChangedNodesSize.get(nodePath);
           Long newDelta = currentDelta + (oldDelta == null ? 0 : oldDelta);
  
           calculatedChangedNodesSize.put(nodePath, newDelta);
        }
  
        for (String path : changesItem.unknownChangedNodesSize)
        {
           unknownChangedNodesSize.add(path);
        }
  
        for (String path : changesItem.asyncUpdate)
        {
           asyncUpdate.add(path);
        }
     }
docs: Merges current changes with new one.