Switch to specialization (or no specialization) without building etc.

[dschrempf]

I am writing this ticket, because nh has replaced nearly all of my custom NixOS related scripts (which is great), but one:

We can use nh os switch -s X or nh os switch -S to build the system, and activate the specialization (next to other side effects).

However, many times, I only want to switch the specialization, without building anything nor changing the boot default.

function switch {
    if [[ $1 == "none" ]]; then
        path="/nix/var/nix/profiles/system"
    else
        path="/nix/var/nix/profiles/system/specialisation/$1"
    fi
    sudo "${path}/bin/switch-to-configuration" test
}

(Note the test part, which only activates the configuration, but does nothing else).

What are your thoughts?

EDIT: I just saw there is nh os test, but it also builds the derivation.