private static @NotNull Collection<VcsRef> collectCommonVcsRefs(@NotNull Stream<? extends VcsRef> stream) {
    MultiMap<VirtualFile, VcsRef> map = MultiMap.create();
    stream.forEach(ref -> map.putValue(ref.getRoot(), ref));

    Stream<Collection<VcsRef>> groups = map.entrySet().stream().map(Map.Entry::getValue);
    return GitBranchUtil.collectCommon(groups, new NameAndTypeHashingStrategy());
  }
private static @NotNull Collection<VcsRef> collectCommonVcsRefs(@NotNull Stream<? extends VcsRef> stream)