@NotNull
  private TreeModelBuilder setVirtualFiles(@Nullable Collection<? extends VirtualFile> files, @Nullable ChangesBrowserNode.Tag tag) {
    if (ContainerUtil.isEmpty(files)) return this;
    insertFilesIntoNode(files, createTagNode(tag));
    return this;
  }
@NotNull
  private TreeModelBuilder setVirtualFiles(@Nullable Collection<? extends VirtualFile> files, @Nullable ChangesBrowserNode.Tag tag)