@Override
  public @Nullable Hash resolveReference(@NotNull String ref, @NotNull VirtualFile root) {
    GitRepository repository = myRepositoryManager.getRepositoryForRoot(root);
    if (repository == null) return null;
    return Git.getInstance().resolveReference(repository, ref);
  }
@Override
  public @Nullable Hash resolveReference(@NotNull String ref, @NotNull VirtualFile root)