For tighter integration with some container registries such as ghcr.io, I want to annotate multi-architecture image indexes. I understand that only media of type application/vnd.oci.image.index.v1+json support annotations. However, I’m unable to create an image index of this type using either Buildah or Podman. Moreover, there doesn’t seem to be a way to annotate image indexes—only images referenced by an index.

Steps to reproduce the issue:

$ buildah manifest create manticore && buildah manifest inspect manticore

Describe the results you received:

f25e51ee5f0a3be38ae63b954aa4a2367c20e514a9f66a007975ee1db8e9a217
{
    "schemaVersion": 2,
    "mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
    "manifests": null
}

Describe the results you expected:

f25e51ee5f0a3be38ae63b954aa4a2367c20e514a9f66a007975ee1db8e9a217
{
    "schemaVersion": 2,
    "mediaType": "application/vnd.oci.image.index.v1+json",
    "manifests": null
}

… because, as I understand it, conformance with OCI specifications is a high priority to Buildah, and Buildah defaults to using the OCI format in other operations, such as committing and pushing images.

Output of buildah version:

Version:         1.31.3
Go Version:      go1.19.12
Image Spec:      1.1.0-rc.3
Runtime Spec:    1.1.0-rc.3
CNI Spec:        1.0.0
libcni Version:
image Version:   5.26.2
Git Commit:
Built:           Fri Aug 25 08:51:43 2023
OS/Arch:         linux/amd64
BuildPlatform:   linux/amd64

In cmd/buildah/manifest.go, the manifest type is currently fixed to manifest.DockerV2ListMediaType.

Could manifest create take a --format option (the same way that push and commit do) and respect the BUILDAH_FORMAT environment variable?

Could manifest annotate annotate the image index directly if (1) the media type is appropriate and (2) no image manifest digest is provided?