Redirect non-www to www for a HTTPS enabled site with web.config?

What is the best way of redirecting non-WWW to WWW for a HTTPS-enabled site (with web.config) without disturbing Googlebot?

I currently have this code in my web.config file:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.webServer>
    <rewrite>
      <rules>
        <rule name="HTTP to HTTPS redirect" stopProcessing="true">
          <match url="(.*)" />
          <conditions>
            <add input="{HTTPS}" pattern="off" ignoreCase="true" />
          </conditions>
          <action type="Redirect" redirectType="Permanent" url="https://{HTTP_HOST}/{R:1}" />
        </rule>
      </rules>
    </rewrite>
  </system.webServer>
</configuration>