Base URL duplicate in internal links when running site under the sub directory

I have a website running in the sub directory for example http://example.com/info.

In the settings.php I have $base_url = 'http://example.com/info'; and in .htaccess I have RewriteBase /info.

When I create a link field and input internal URL (eg. user/login), I get a result with base URL duplicate (eg. http://example.com/info/info/user/login).

This is happening because in the _link_sanitize() function on line 517 we have the following code:

  if (!empty($url_parts['url'])) {
    $item['url'] = url($url_parts['url'],
      array('query' => isset($url_parts['query']) ? $url_parts['query'] : NULL,
      'fragment' => isset($url_parts['fragment']) ? $url_parts['fragment'] : NULL,
      'absolute' => !empty($instance['settings']['absolute_url']),
      'html' => TRUE,
      )
    );
  }

The link URL gets sanitized and converted into /info/user/login because of the url() function and then, when its processed by the theme_link() at the end, the Drupal will add /info again.