schema: Limit schemaVersion to 2 and enumerate mediaType

[wking]

For manifests and manifest lists, to match the requirements from their Markdown definitions.

[xiekeyang]

@wking

1. Do you forget to refresh the generated virtual file system, to see https://github.com/opencontainers/image-spec/blob/master/HACKING.md#virtual-schema-httpfilesystem?
2. It seems that you want to reject all media types in compatibility-matrix, that may be conflict to our previous conclusion. I worry that we fall into the confusion again that media type should be loose or strict. After read Intra-blob JSON validation correctness and image-spec release policy #406 , I still think this PR is too strict.

[wking]

On Thu, Oct 20, 2016 at 09:48:41PM -0700, xiekeyang wrote:

1. Do you forget to refresh the generated virtual file system…

Oops, yeah. Fixed with the just-pushed 00f177b.

1. It seems that you want to reject all media types in compatibility-matrix…

I think there are two things going on here: what you are and what you reference. #304 is about who you reference, and the pattern is that we require implementations to support appropriate OCI types but allow images and implementations to use other types as well. This PR, on the other hand, is about declaring what you are, and there's only one good answer for that.

An application/vnd.oci.image.manifest.v1+json with application/vnd.docker.container.image.v1+json in config.mediaType is legal (although there may be compliant runtimes that don't support it). An application/vnd.oci.image.manifest.v1+json with application/vnd.docker.distribution.manifest.v2+json in mediaType is not legal.

[wking]

I've just pushed an additional commit (801699e) fixing the convertFormats direction to make Travis happy, so this stricter checking has already been useful :).

[vbatts]

needs a rebase

[wking]

On Tue, Nov 01, 2016 at 07:51:41AM -0700, Vincent Batts wrote:

needs a rebase

Rebased around #413's schema/fs.go bump with 801699e → c23165c.

[philips]

LGTM

Conflict though.

[wking]

On Wed, Nov 16, 2016 at 02:38:58PM -0800, Brandon Philips wrote:

Conflict though.

Rebased onto master and rebuilt schema/fs.go with c23165c → dad01a1.

It's probably best if you order up all the JSON-Schema-touching PRs
(maybe tag them all?), because all of them are going to conflict on
fs.go.

An alternative would be to ask contributors to not update fs.go and
have the merging maintainer rebuild fs.go after merging the change.
In this case you'd also want to add a Travis line rebuilding fs.go
before running the tests.

[philips]

LGTM

ptal @opencontainers/image-spec-maintainers

[stevvooe]

LGTM