My understanding of the `stage` and `prime` directives are that they let you specify: * stage: what files go from `$CRAFT_PART_INSTALL` to `$CRAFT_STAGE` * prime: what files go from `$CRAFT_STAGE` to `$CRAFT_PRIME` and that, if omitted, the default behaviour is to copy everything in each of those locations. It would be great to have this explained more in the docs. There's a few hints at this, but I don't see anything that explicitly describes the behaviour (especially the default behaviour). I found it awkward to learn how to use these when I'd see some `rockcraft.yaml` files using `stage` and `prime`, and others omitting them entirely.