@Nullable
 public static String getRelativePath(
     @NotNull String basePath,
     @NotNull String filePath,
     final char separator,
     final boolean caseSensitive) {
   return FileUtilRt.getRelativePath(basePath, filePath, separator, caseSensitive);
 }
 @Nullable
 public static String getRelativePath(
     @NotNull String basePath, @NotNull String filePath, final char separator) {
   return FileUtilRt.getRelativePath(basePath, filePath, separator);
 }
 @Nullable
 public static String getRelativePath(File base, File file) {
   return FileUtilRt.getRelativePath(base, file);
 }