@Nullable
  @Contract(pure = true)
  public static String getRelativePath(@NotNull String basePath, @NotNull String filePath, char separator) {
    return getRelativePath(basePath, filePath, separator, SystemInfoRt.isFileSystemCaseSensitive);
  }
@Nullable
  @Contract(pure = true)
  public static String getRelativePath(@NotNull String basePath, @NotNull String filePath, char separator)