Create custom search for contacts in Groups A,B,C but not in Groups X,Y,Z

There is the UI and a start for this at: CRM/Contact/Form/Search/Custom/Group.php. The SQL is incorrect. We will need to use temporary tables etc to make this efficient. You can get the queries from the Mailing code CRM/Mailing/BAO/Mailing.php, function getRecipients

Once this is done, can you get file another issue and get someone else to do the same thing for Tags