Yet Another Harring Random Notes File (henceforth known as YAHRF)

portage.ebuild.ebuild_repository is unconfigured packages, with the reasoning that as a repo, it's not supposed to know 
about config crap (encapsulation); you wrap it with a configurator, which wraps the base package with configuration data, 
generated a flattened *depends, src_uri, license, keywords, etc.

The issue is how to handle restrictions coming in that change the wrapper.
( ( x in use ) and AlwaysFalse ) || ( x not in use )
^^^ how to handle this?  Effectively the wrapper needs resetting, but that probably won't work perfectly either.
need to break it down into a tree of non-modifying restrictions
stack based cmatch?
push/pop modifications?

here's how we do it.
running count of changes on a configurable pkg
each restriction that holds sub restrictions (recursive, think AndRestrictionSet fex), grabs a counter from the pkg, 
if failed run, unwinds changes down to the level it saw, and pukes the pkg back if negate, or None