Docker type version_definition: image id or registry digest

[jayniz]

Question about this line from the docker type spec:

  "version_definition": {
    "requirement": "optional",
    "note": "The version should be the image id sha256 or a tag. Since tags can be moved, a sha256 image id is preferred."
  },

Is this really supposed to be the image id (the sha256 of the image's config.json) or is the intended value the registry digest (the sha256 of the manifest on the registry, which includes the config.json)? The latter is the thing you see when you docker pull an image, and the common way to content-address images, e.g. hub.docker.com/foo/bar@sha256:...

[pombredanne]

@jayniz Thanks! ... Let me dive in there, I think you are correct that this should be the latter.