post_upgrade() {
    local breakpoints=(
        2.9.0-1
    )

    for v in "${breakpoints[@]}"; do
        if [[ $(vercmp "$v" "$2") -eq 1 ]]; then
            "_${v//[.-]/_}_changes"
        fi
    done
}

_2_9_0_1_changes() {
    cat << EOF
It was found that you were upgrading from old-devtools package to the new one, which requires manual intervention:

* make sure that devtools are upgraded to the latest release;
* merge service configuration if required;
* run setup command (i.e. sudo ahriman service-setup) with the same arguments as you did before;
* remove build chroot: sudo rm -r /var/lib/ahriman/chroot/ahriman-x86_64/;
* update local databases: sudo -u ahriman ahriman update --no-aur --no-local --no-manual -yy;

For more information kindly refer to changelog https://github.com/arcan1s/ahriman/releases/tag/2.9.0
EOF
}