public static @NotNull Map<VirtualFile, Set<VcsRef>> groupRefsByRoot(@NotNull Collection<? extends VcsRef> refs) {
    Map<VirtualFile, Set<VcsRef>> map = new TreeMap<>(Comparator.comparing(VirtualFile::getPresentableUrl));
    for (VcsRef item : refs) {
      map.computeIfAbsent(item.getRoot(), k -> new HashSet<>()).add(item);
    }
    return map;
  }
public static @NotNull Map<VirtualFile, Set<VcsRef>> groupRefsByRoot(@NotNull Collection<? extends VcsRef> refs)