Very simple logrotate like script to create 8 backups before deletion

backshift.sh

#!/usr/bin/env bash

readonly backlevel=8

backshift() {
  local target="${1:?}"
  local cdown=$((backlevel+1))
  local work=

  # No shift if there is no input
  [[ ! -e "${target}" ]] && return 1

  while ((--cdown)) ; do
    work="${target}.${cdown}"
    [[ -e "${work}" ]] || continue
    case "${cdown}" in
      "${backlevel}")
        rm -f "${work}" ;;
      *)
        mv "${work}" "${target}.$((cdown+1))" ;;
    esac
  done
  mv "${target}" "${target}.1"
}

backshift "${1:?}"