public static @Nullable String getDocUrl(@NotNull VirtualFile root, String relPath) {
    if (root.getFileSystem() instanceof HttpFileSystem) {
      @NonNls String url = StringUtil.trimEnd(root.getUrl(), "/index.html", true);
      if (!url.endsWith("/")) {
        url += "/";
      }
      return url + relPath;
    }
    else {
      VirtualFile file = root.findFileByRelativePath(relPath);
      return file == null ? null : file.getUrl();
    }
  }
public static @Nullable String getDocUrl(@NotNull VirtualFile root, String relPath)