public static List<String> toRelativeFiles(@NotNull VirtualFile root, @NotNull final Collection<? extends VirtualFile> files) {
    ArrayList<String> rc = new ArrayList<>(files.size());
    for (VirtualFile file : files) {
      rc.add(relativePath(root, file));
    }
    return rc;
  }
public static List<String> toRelativeFiles(@NotNull VirtualFile root, @NotNull final Collection<? extends VirtualFile> files)