See also docker-library/bashbrew#51: the most important call-out here is that this is intended for base images where we're effectively swapping a super-basic three-line Dockerfile (FROM scratch + ADD rootfs.xxx / + CMD ["..."]) that creates rootfs metadata as a side effect for an explicit JSON file that contains the pre-calculated metadata such that an architecture image's individual content-addressable digest is preserved all the way through our pipeline.

This is not intended for non-base images, and new images / image updates which attempt to do so will likely be rejected during review.