frequent package rebuilds (slow and wasteful) #30
Description
Currently, packages are rebuilt often for no good reason. They don't really have a sense of when their inputs changed meaningfully. There's no distinction between:
- packaging up the same exact thing,
- packaging up a thing that's equivalent but has a fresher cache,
- packaging up a new thing that's really not that different for downstream, and
- packaging up a new thing that's critically different for downstream (like a security fix).
They also have no good way of maintaining caches when their inputs do change, so they redo most or all of their work when that happens.