Signing built images

Users can sign images produced with ko publish using tools like cosign.

For example:

$ cosign sign -key cosign.key $(ko publish ./)

ko resolve produces potentially many images, which makes this a bit harder. You could ko resolve then scan the resulting YAML for ko-built image references and sign all of those with some bash magic, but .

Would it be useful to have a ko resolve --sign cosign.key flag that used the provided key to sign all images built during ko resolve?

ko publish --sign cosign.key could also be a convenience alias for, effectively, cosign sign $(ko publish), which wouldn't require users to have cosign installed.

@dlorenc good idea? bad idea?