Context

Fixes dotnet/sdk-container-builds#609

This is a feature request from partner team - support publishing multi-arch OCI image as one combined tarball. Currently we publish separate tarballs for each architecture.

Customer impact

Without this feature customers will not be able to export multi-arch OCI image as one combined tarball, they will get separate tarballs for each architecture, and will have to combine them manually to achieve this.

Details

Current behavior for multi-arch image publishing

• remote registry - create single-arch image for each arch and publish them to the remote registry, then create image index based on them and load to remote registry
• local daemon (docker/podman) - create single-arch image for each arch and publish them to the local daemon
• tarball - create single-arch image for each arch and publish them as separate tarballs

Behaviour after this PR

• remote registry - create single-arch image for each arch and publish them to the remote registry, then create image index based on them and load to remote registry (same as before)
• local daemon (docker) - create one multi-arch image and publish it to the local daemon
• local daemon (podman) - create single-arch image for each arch and publish them to the local daemon (same as before; support for podman will be added in the future)
• tarball - create one multi-arch image and publish it as a tarball

Note: in order to load a multi-arch oci image tarball, containerd image store should be enabled for Docker.

Changes made

1. Added support for multi-arch OCI tarballs creation in DockerCli.
2. Refactored the code to extract publishing logic from CreateNewImage task into a separate class, to be able to reuse it in CreateImageIndex task.
3. Added SkipPublishing parameter in CreateNewImage task, in order to create an image but skip publish it (this is needed for multi-arch tarball publishing because we need to publish one combined tarball)
4. More refactoring

Testing

Modified end to end multi-arch tests to reflect the new behavior. Tested manually as well.

Risks

Low - new tests ensure the scenarios are now covered, the existing tests ensure that other scenarios were not affected.