permit updates to fields on the far side of joins

[Robert Collins]

We have this code in LP today:

            for attachment in self.attachments:
                attachment.libraryfile.restricted = private

This is in bug.py.

We should be doing a bulk update there, but we have to resort to a manual query to do that, yet storm knows the relationships involved. (self.attachments is a resultset)

I'd like to be able to write:
self.attachments.libraryfile.restricted = private
or
self.attachments.set('libraryfile.restricted'=private)
or something along those lines. Basically not having to repeat the relationship just because we're doing a bulk update.