public @Nullable WatchRequest addRootToWatch(@NotNull String rootPath, boolean watchRecursively) {
    Set<WatchRequest> result = addRootsToWatch(singleton(rootPath), watchRecursively);
    return result.size() == 1 ? result.iterator().next() : null;
  }
public @Nullable WatchRequest addRootToWatch(@NotNull String rootPath, boolean watchRecursively)