@aboch looks like issues

Not sure about vendor failure:

00:33:28 hack/dind: line 29: /go/src/github.com/docker/docker/hack/validate/vendor: No such file or directory
00:33:29 Build step 'Execute shell' marked build as failure

It looks like it is looking for the validate directory that was added for the new vendoring, which is not present in 1.12.x branch.

experimental is failing because in 1.12, plugins are still in experimental.

The media type for plugins was changed in 1.13 to application/vnd.docker.plugin.v1+json https://github.com/docker/distribution/blob/4ad885a6725bfca9ea00bd87341e367c0f919560/manifest/schema2/manifest.go#L21. As a result, the sample plugin we use in integration tests tiborvass/no-remove was re-pushed to Hub using this new mediatype.

That's why the tests are failing. We have 2 options:

1. Backport the plugin mediatype changes to 1.12.x
2. Repush a 1.12 version of tiborvass/no-remove that has the old mediatype and update the tests to use it.

I prefer (1)

For the plugin mediatype changes, we need 970b23d

An easier option is to simply add the new media type here https://github.com/aboch/docker/blob/76d2f1f29bbc11c92ab20489fc5eee2593b6d879/plugin/distribution/types.go#L16. Then use both the new and the old type for checking in https://github.com/aboch/docker/blob/76d2f1f29bbc11c92ab20489fc5eee2593b6d879/plugin/distribution/pull.go#L146

@johnstep can you please try this one, since there is no CI for 1.12.x on Windows

LGTM on Windows. It built successfully on Windows (for Windows) and all unit tests passed. I rebuilt and tested again with the resulting binaries, and that succeeded.

All experimental tests are failing due to the known plugin mediatype issue. It can be fixed by updating the code to accommodate to the expected media type of the sample plugin. Or the sample plugin can be re-pushed by @tiborvass

In either case, this PR can be merged, since the failing tests are unrelated to the PR.

LGTM ping @LK4D4 @tonistiigi

@anusha-ragunathan Thanks for your help in trying to solve the experimental failure on 1.12.x.
Given it is currently broken, I feel it would be more efficient if you guys address the plugin failure on experimental ci issue via a separate PR. Will also give you more control over what to change. After that is merged we can rebase our vendoring (libnetwork/swarmkit) PRs .
I went ahead and removed the uncomplete media type changes commit from this PR.

@aboch : Yessir! #29089

@tonistiigi windows is expected to fail

#29089 handles the experimental failures.

LGTM