_ahfail_msg() {
    cat <<'MSG'
==> ahfail is its own screen locker and uses its own PAM service (/etc/pam.d/ahfail).
    Nothing in your other PAM files has been changed.

    Check your setup:      ahfail doctor
    See the effect safely: ahfail test
    Lock the screen:       ahfail

    Lock automatically:
      Wayland: swayidle -w timeout 300 'ahfail' before-sleep 'ahfail'
      X11:     xss-lock -- ahfail

    The old PAM hook (auth optional .../libahfail_pam.so in e.g. /etc/pam.d/i3lock)
    is no longer needed with `ahfail`. Remove that line yourself if you added it.
MSG
}

post_install() {
    _ahfail_msg
}

post_upgrade() {
    # Only when coming from before 0.10.0, when ahfail became its own locker;
    # repeating the message on every update would just teach people to skip it.
    if (( $(vercmp "$2" 0.10.0) < 0 )); then
        _ahfail_msg
    fi
}