Unknown usage for --config option

[nak3]

This is kind of question and bug report.

Although kn command has --config option, no docs explain how to
use it - how we can configure.kn.yaml. It looks like the option cannot be used?

$ kn service -h
  ...
Global Flags:
      --config string       config file (default is $HOME/.kn.yaml)

Also, once we put a file in ~/.kn.yaml, we always get spam logs as
Using config file: /home/knakayam/.kn.yaml.

(e.g)

$ touch ~/.kn.yaml

$ kn service list
Using config file: /home/knakayam/.kn.yaml      <-  GETS THIS MESSAGE  EVERYTIME
hello-example