TLDR: Introduce a restartPolicy field to init containers and use it to indicate that an init container is a sidecar container. Kubelet will start init containers with restartPolicy=Always in the order with other init containers, but instead of waiting for its completion, it will wait for the container startup completion.
Yep, it’s also alpha, under intense development, and by every account (including those vendors who are chomping at the bit to start selling it to customers) absolutely not production ready.
You can use it through kubeconfig.