# exists, use 2).
# NOTE: conversion of some characters in the filename could
# result in an unintended name collision. If that is a concern,
# exists, use 2).
# NOTE: conversion of some characters in the filename could
# result in an unintended name collision. If that is a concern,
# be the basis for a remedy.
# 2) Concatenation of BACKUP_PREFIX and input filename.
# NOTE: if a file of that name already exists in the destination
# be the basis for a remedy.
# 2) Concatenation of BACKUP_PREFIX and input filename.
# NOTE: if a file of that name already exists in the destination