[morelisp]

> So where do these binaries get built and how does the system know which binaries to rebuild for a given change?

By the CI. All major CI/CD tools support rules like build binary x whenever a file under x-src/* changes; commit binary x when the ref matches /v[0-9.]+/; don't allow developers to manually push to these refs / paths; (run a script to) bump the dependent x of y whenever binary x changes; merge the bumped version if all tests still pass; etc.

[weberc2]

The problem is dependency graphs aren’t strictly hierarchical, so it doesn’t suffice to say “rebuild whenever something under this directory changes”.