DockerHub tags include windows images, but manifests are missing

[squaremo]

Following the docker registry API, when retrieving image metadata from an image registry, we first ask for all the tags, then for each tag, ask for the manifest addressed by that tag.

For some images (e.g., nats), the tags include images built for windows (e.g., nats:1.0.4-nanoserver), but the manifests implied are not available and we get 404. But in general, we don't know that this is because it refers to a windows image -- the tag is just a string.

It turns out that for (at least) some library images, a manifestlist is used. You need to explicitly ask for it using an Accept header, as for schema v2. The resulting document gives a list of manifests, surprise, of which you can choose which you want.

We'll have to figure out how to deal with this extra indirection.

[squaremo]

NB we handle manifestlists as of #851; however, if there's no linux/amd64 image, it's counted as a failure, and the whole image list abandoned. So it's not yet ideal.

[rade]

Isn't this a dup of #741 now?

[squaremo]

Isn't this a dup of #741 now?

Yes, the remaining bit of this is the thing we need to fix for #741 to be closed.