stack-based configuration files road-map

[Martin Pool]

That sounds great.

The 'load it just once' probably means tying the configuration objects
to the library state object.

One other thing has been on my mind, which is handling configuration
and isolation during testing:

 * in (nearly?) every case, we want tests to run totally isolated from
the configuration of the user running the tests; having all
configuration go through a single patch will let us clean up some code
that does that, but it also may mean the stack itself needs to be
isolated
 * since the tests don't care about the user's configuration, they
don't really need to go to a file on disk
 * it would be useful to have a clean way for tests to see what
happens when a particular value is configured
 * some tests for configuration itself will be exceptions

Martin