Perhaps this bug and bug #458789 have a similar goal. The watchfile could look like this.
# Run a script (such as debian/rules) to download the orig tarball use-download-script=debian/rules \ use-download-script-options="get-orig-source" -- Regards, Andres Mejia -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]