Add btrbk

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

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

@@ -13,11 +13,22 @@ mount "$DEVICE" /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/$timestamp"
+  timestamp=$(date --date="@$(stat -c %Y /mnt/btrfs/@)" "+%Y%m%dT%H%M")
+  base="@.$timestamp"
+
+  target="/mnt/btrfs/@.bak/$base"
+  if [[ -e "$target" ]]; then
+    i=1
+    while [[ -e "/mnt/btrfs/@.bak/${base}_$i" ]]; do
+      (( i++ ))
+    done
+    target="/mnt/btrfs/@.bak/${base}_$i"
+  fi
+
+  mv /mnt/btrfs/@ "$target"
 fi
 
-find /mnt/btrfs/@.bak/ -maxdepth 1 -mtime +14 | while IFS= read -r i; do
+find /mnt/btrfs/@.bak/ -maxdepth 1 -mtime +7 | while IFS= read -r i; do
   delete_subvolume_recursively "$i"
 done