oci-mediatypes not defaulting to true if no attestations/annotations in image exporter #6094
Description
Contributing guidelines and issue reporting guide
- I've read the contributing guidelines and wholeheartedly agree. I've also read the issue reporting guide.
Well-formed report checklist
- I have found a bug that the documentation does not mention anything about my problem
- I have found a bug that there are no open or closed issues that are related to my problem
- I have provided version/information about my environment and done my best to provide a reproducer
Description of bug
Bug description
Although by the docs oci-mediatypes should default to true, it only does so if user does not pass --provenance=false in docker buildx build.
OCI exporter seems to work correctly as it is initialized with default value in https://github.com/moby/buildkit/blob/master/exporter/oci/export.go#L73 but image exporter only configures oci-mediatypes if user passed oci-mediatypes attribute https://github.com/moby/buildkit/blob/master/exporter/containerimage/opts.go#L52.