public @Nullable VcsUser getOrReadUser(@NotNull VirtualFile root) {
    VcsUser user = myUserMap.get(root);
    if (user == null) {
      user = readUser(root);
      if (user != null) {
        myUserMap.put(root, user);
      }
    }
    return user;
  }
public @Nullable VcsUser getOrReadUser(@NotNull VirtualFile root)