maintaining muddle feels a bit like being davros

As a result of some recent changes to muddle - mainly tibs's code - you can now merge two build trees (which we call domains) into a single overarching build tree.
I've now added a couple of bits (check out r243) and I have a bit of a port of an ASTB build tree and a client's STB stack running.
With the addition of a couple of simple hooks on each side, I can write 100 lines of python which automatically checks out two entirely unrelated build trees, merges them together, builds them both (on demand, checking out code from various repositories in git, svn, and bzr, and supplying the right kernel includes across the boundary) and then merges the resulting filesystems. On demand.
It's not finished yet, but it's quite impressive to watch it go.