serialization: remove combined spec

[philips]

The combined spec isn't really part of the image format and introduces
new objects that we don't have a schema for. Largely I think that it
should be replaced by something like the image layout.

#94
Signed-off-by: Brandon Philips brandon.philips@coreos.com

[philips]

This is from a discussion with @stevvooe and @wking that is outlined in #92.

cc @vbatts @opencontainers/image-spec-maintainers

[wking]

+1 to this (#94 is a nicer way to accomplish the same goal).

How does removing it square with backwards-compat 1? Maybe you
should be deprecating instead of removing?

[philips]

@wking AFAIK this combined format is never used on the wire anywhere. It is only in docker save/load.

[wking]

On Fri, May 27, 2016 at 12:23:05PM -0700, Brandon Philips wrote:

@wking AFAIK this combined format is never used on the wire
anywhere. It is only in docker save/load.

I'm not sure how far image-spec's compatibility goal extends ;). #94
is doing the same sort of thing, so it seems like the idea is in
scope for image-spec. Supporting something like #94 but not the old
Docker equivalent sounds like a broken backwards-compat.

Personally, I'm not really a backwards-compat-in-the-spec guy ;). As
long as the spec calls for appropriate identifiers, external tooling
can provide the backwards-compat (e.g. an archive unpacker that
recognizes and unpacks both the old Docker format and the new #94).
But I'm not sure where the image-spec maintainers stand on that sort
of thing.

[stevvooe]

The implication here is that we lose compatibility with the docker save format.

For testing purposes, OCI (tools or here) should have a way of processing docker save files into the OCI image format, but I am split on whether or not we want to "lock down" the docker save format. The main issue being that it is an organic format, with several subtleties, making a correct specification challenging.

The format in #94 is wildly better, but we really need to leverage the existing tools for bootstrap of OCI.

I do however agree that this doesn't really belong in the image config specification.

[philips]

@stevvooe Is there a library or something for parsing all of those formats in docker save/load? We can certainly put them into oci-image-tool. Would you be OK merging this PR if I filed an issue to add that as an oci-image-tool feature?

[stevvooe]

@philips The package is here.

Would you be OK merging this PR if I filed an issue to add that as an oci-image-tool feature?

That sounds reasonable. We may want to add some language about translation to target formats for backwards compat for the packed archive in #94.

[philips]

OK, I will add language to #94. Wanna LGTM this?

[stevvooe]

LGTM

[jonboulle]

LGTM