slightly dubious plan for splicing trees back together
slightly dubious plan for splicing trees back together

this doesn't seem right; we have no frame predicate into which
we can conveniently fold away things as we run down the tree..
we should probably ask Adam what's the right pattern for this
kind of situation.

mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl