Allow building OCI tars with multiple tags.

[TadCordle]

This should just a matter of replacing

index.addManifest(manifestDescriptor, imageReference.toStringWithTag());

with

for (String tag : allTargetImageTags) {
  index.addManifest(manifestDescriptor, imageReference.withTag(tag).toStringWithTag());
}

in ImageTarball. Just need a way to test that it works before doing this.

Relevant: opencontainers/image-spec#796, containers/libpod#4646.

[lfarkas]

what about this issue?

[chanseokoh]

@lfarkas podman doesn't support this (https://github.com/containers/libpod/issues/4646). We may go ahead and do this, but there's no way to know if this ever works. Are you aware of any tool that can accept an OCI tar format other than podman?

[lfarkas]

no we use podman...and we can wait until it'll be fixed.

[TadCordle]

FYI the podman issue is here: https://github.com/containers/libpod/issues/4646