Add min_keep parameter

bashclub-zsync/usr/bin/bashclub-zsync

@@ -32,6 +32,9 @@ subvol_source="inherited|received"
 # pipe separated list of snapshot name filters
 snapshot_filter="hourly|daily|weekly|monthly"
 
+# minimum count of snapshots per filter to keep
+min_keep=3
+
 usage() {
 	cat >&2 <<-EOF
 	usage: $prog [-h] [-d] [-c CONFIG]
@@ -69,10 +72,11 @@ else
     cat << EOF > $conf
 target=$target
 source=$source
-sshport=22
+sshport=$sshport
 tag=$tag
 subvol_source="$subvol_source"
 snapshot_filter="$snapshot_filter"
+min_keep=$min_keep
 EOF
     log "Initial config file created. Please adjust and restart script. Exiting..."
     usage 0
@@ -158,9 +162,17 @@ for name in "${syncvols[@]}"; do
     for interval in $filter ; do
         guid=$($ssh $sshcipher $sshport $source "zfs list -H -o guid,name -S creation -t snapshot $name | grep $interval | cut -f1 | tail -1")
         if [[ "$(echo -e "$guid" | sed 's/\n//g')" != "" ]]; then
-            for snap in $($zfs list -H -o name,guid -S creation -t snapshot $target/$name | grep $interval | grep --after-context=200 $guid | grep -v $guid | cut -f1); do
+            snaps_to_delete=$($zfs list -H -o name,guid -S creation -t snapshot $target/$name | grep $interval | grep --after-context=200 $guid | grep -v $guid | cut -f1)
+            delete_count=$(echo $snaps_to_delete | wc -l)
+            for snap in $snaps_to_delete; do
+                if [[ $delete_count -gt $min_keep ]]; then
                     log "Deleting $snap"
+                    if [[ $debug == "-v" ]]; then log "[DEBUG] delete_count=$delete_count, min_keep=$min_keep"; fi
                     $zfs destroy $debug $snap
+                    delete_count=$(expr $delete_count - 1)
+                else
+                    if [[ $debug == "-v" ]]; then log "[DEBUG] Skipping deletion of $snap. delete_count=$delete_count, min_keep=$min_keep"; fi
+                fi
             done
         fi
     done