buildtool/linux/tools/x86_64-linux-gnu/sysroot/lib/recovery-mode/options/apt-snapshots

#!/bin/bash

set -e

. /lib/recovery-mode/l10n.sh

# check if its there
if [ ! -x /usr/bin/apt-btrfs-snapshot ]; then
    exit 1
fi

# check if its usable, if list returns a non-zero exit code, 
# we probably run on a system with no snapshot support
if ! /usr/bin/apt-btrfs-snapshot list > /dev/null  2>&1; then
    exit 1
fi

# if we make it to this point, show some help
if [ "$1" = "test" ]; then
    echo $(eval_gettext "Revert to old snapshot and reboot")
    exit 0
fi

# get snapshots and show them in whiptail
snapshots=$(apt-btrfs-snapshot list | sed 1d)
tag_item=""
for item in $snapshots; do
    tag_item="$item snapshot $tag_item"
done

choice="$(whiptail --menu "$(eval_gettext "Snapshot")" 15 70 6 $tag_item \
         3>&1 1>&2 2>&3 3>&-)"
# user selected cancel
if [ -z "$choice" ]; then
    exit 0
fi

# set new snapshot and reboot
if apt-btrfs-snapshot set-default "$choice"; then
    reboot
fi