If you had previously received an error exporting cache which looks like this:
------ > exporting cache: ------ failed to solve: rpc error: code = Unknown desc = error writing manifest blob: failed commit on ref "sha256:...": unexpected status: 400 Bad Request
That export cache command will now succeed as expected and ghcr.io will serve the build cache when used as
cache-from during building as well.
For example this buildx command uses
docker buildx build --progress plain --load f Dockerfile -t ghcr.io/github/container-registry-playground:build-x --pull --cache-from=type=registry,ref=ghcr.io/github/container-registry-playground:build --cache-to=type=registry,ref=ghcr.io/github/container-registry-playground:build,mode=max .