opam repo add: silence warning when --this-switch is explicitly passed

[emillon]

Hi,

When using opam repo add NAME URL, the following message gets printed:

Repository NAME has been added to the selections of switch SWITCH only.
Run `opam repository add NAME --all-switches|--set-default' to use it in all existing switches, or in newly created switches, respectively.

I would expect that explicitly passing --this-switch (equivalent to the default behavior) would silence this warning, but that is not the case. There does not seem to be a way to silence it.

What do you think about printing the warning only if this behavior is selected by default?

For context, the mirage 4 client is generating this in build scripts.