Views other than contact don't join all tables

When creating a view other than a civicrm_contact view, but one that joins to contacts (like one for event participants, contributions, etc.), not all contact information carries over. For example, there's a "Group(s)" field that tries to select the non-existent field civicrm_contact.groups, and custom fields are attempted to be selected as civicrm_contact.custom_X.

I've attached a patch to civicrm.views.inc that covers views and tags, doing the joins just like for civicrm_contact. However, I'm not entirely sure how to take care of the custom fields, especially to hide them from showing up as if they're in the civicrm_contact table.