Joking aside, versioning and controlled
continuous mutation was a solved problem
in computer science (by MIT) years before
Unix came into being.
Alas, it's mostly forgotten. So I
typed in a Paul Stachour Multics paper,
"Observations about Software Maintenance",
available at http://multicians.org/stachour.html
Having used it myself (in C) to avoid flag-days,
I can happily recommend it to the Python folks.