I added a warning to the Kubernetes/Deployments wikitech page.
But maybe we could also consider a small shell script that provides a warning and a prompt on the server before calling helmfile, so e.g. we'd tell people to run a script called wm-helmfile:
$ wm-helmfile -e eqiad -i apply --context 5 $ NOTE: The output of this command can contain sensitive information like usernames and API keys. Use caution when sharing its output. Continue? (y/n) $ {helmfile is invoked with arguments}
Other ideas to warn/notify people in context of the command they are running?
The context for this task is T332598.