Mon Nov 26 16:03:05 EST 2018

A rebuild should export a dependency list

This is the insight, and probably what "redo" is about.

The reason why build systems do not compose, is that the dependency
list gets lost.  There is a need to re-trigger the black box when the
coars-grain dependencies change.

So, rebuild builds:
- product
- dependency list
- rebuild script

With this identified, it is also possible to overapproximate it.