Add custom impermanence module

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/system/configs/impermanence/scripts/wipe.sh

@@ -0,0 +1,25 @@
+delete_subvolume_recursively() {
+  IFS=$'\n'
+  for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
+    delete_subvolume_recursively "/mnt/btrfs/$i"
+  done
+  btrfs subvolume delete "$1"
+}
+
+mkdir -p /mnt/btrfs
+mount /dev/mapper/luks /mnt/btrfs
+
+if [[ -e /mnt/btrfs/@ ]]; then
+  mkdir -p /mnt/btrfs/@.bak
+  timestamp=$(date --date="@$(stat -c %Y /mnt/btrfs/@)" "+%Y-%m-%d_%H:%M:%S")
+  mv /mnt/btrfs/@ "/mnt/btrfs/@.bak/$timestamp"
+fi
+
+find /mnt/btrfs/@.bak/ -maxdepth 1 -mtime +14 | while IFS= read -r i; do
+  delete_subvolume_recursively "$i"
+done
+
+btrfs subvolume create /mnt/btrfs/@
+
+umount /mnt/btrfs
+rmdir /mnt/btrfs