post_upgrade() {
    local breakpoints=(
        2.9.0-1
        2.12.0-1
    )

    for v in "${breakpoints[@]}"; do
        if [[ $(vercmp "$v" "$2") -ne "-1" ]]; then
            "_${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 migration notes https://ahriman.readthedocs.io/en/stable/migration.html
EOF
}

_2_12_0_1_changes() {
    cat << EOF
Whereas old tree is still supported it is highly recommended to migrate to the new one:

* stop and disable all services;
* run service-tree-migrate as ahriman user;
* edit configuration to avoid pointing to the old paths;
* update devtools pacman configuration (e.g. /usr/share/devtools/pacman.conf.d/ahriman-x86_64.conf) with new repository path;
* update synchronization services in order to support new paths (or setup redirects);
* enable web and timer services again by using x86_64-aur-clone suffix, where x86_64 is your architecture and
  aur-clone is repository name;

For more information kindly refer to migration notes https://ahriman.readthedocs.io/en/stable/migration.html
EOF
}