public static String calcRelativePath(VirtualFile parent, VirtualFile child) {
    String result = FileUtil.getRelativePath(parent.getPath(), child.getPath(), '/');
    if (result == null) {
      MavenLog.LOG.warn("cannot calculate relative path for\nparent: " + parent + "\nchild: " + child);
      result = child.getPath();
    }
    return FileUtil.toSystemIndependentName(result);
  }
public static String calcRelativePath(VirtualFile parent, VirtualFile child)