Extend docker container update to support updating ports

[AkihiroSuda]

Description

Motivation

Usernetes Gen2 (Kubernetes in Rootless Docker) currently requires all the ports to be hard-coded in docker-compose.yaml, and the port list cannot be updated without restarting the entire Kubernetes node container:
https://github.com/rootless-containers/usernetes/blob/gen2-v20240410.0/docker-compose.yaml#L13-L21

Extending docker container update to support modifying ports will allow dynamically updating the port list without restarting the entire Kubernetes node container.

This should be useful for other Kubernetes-in-Docker, Docker-in-Docker, and similar stacks.

CLI syntax designs

Option A: docker container update CONTAINER --add-publish=NEWPORT

Example: remove 8080:81, keep 8081:81 untouched, add 8082:82

docker container run --name=foo -p 8080:80 -p 8081:81 foo
docker container update foo --remove-publish=8080 --add-publish=8082:82

Example: remove all the ports

docker container update foo --remove-publish=8081 --remove-publish=8082

Option B: docker container portx add CONTAINER NEWPORT

Example: remove 8080:81, keep 8081:81 untouched, add 8082:82

docker container run --name=foo -p 8080:80 -p 8081:81 foo
docker container portx remove foo 8080
docker container portx add foo 8082:82

Example: remove all the ports

docker container portx remove foo 8081 8082

Option C: docker container update CONTAINER --publish=PORT ...

Example: remove 8080:81, keep 8081:81 untouched, add 8082:82

docker container run --name=foo -p 8080:80 -p 8081:81 foo
docker container update foo -p 8081:81 -p 8082:82

Example: remove all the ports

docker container update foo -p none

[Anish-M]

Hi, working on this issue right now, the client api to update using updateConfig doesn't have PortBindings as a field in the updateConfig struct and the only way to update the ports is by calling ContainerUpdate with a modified host Config on the daemon, do you know how I could get the daemon object from the daemon string?