network_mode: "service:[service name]" not adequately documented.

[vinilneves]

@ the docs it reads

Network mode. Use the same values as the docker client --network parameter, plus the special form service:[service name].

But I can't find anything that clearly states what it's supposed to do, just guesses and vague answers.

Same as https://github.com/docker/docker.github.io/issues/5325 But someone closed it and said "feel free to reopen it" but ignored when people asked to reopen.