Very neat idea, questions about "opaque"/output in repo

[daverosoff]

Rob—this is a nice looking project. It's another step toward what I have dreamed of since Alex J. once whispered the phrase "Beezer code" to me, an open source course that can emerge fully formed, like Minerva from the brow of Jove. I have a question: do you think there is any way to make the build truly idempotent? It seems like the .pdf and .sagews files—but not the .ipynb—will change with every build (something you avoided for HTML via --stringparam debug.datedfiles no. Feel free to respond via email if you prefer; I started an issue thinking other users might have the same question.