#!/usr/bin/env sh
# YES_ZSH

baknow() { ### @-
    ### backup a single file by appending its timestamp given by [`now`.](#now)
    ###
    ### ```
    ### $ touch -d '2001-12-25 16:30:00' butts
    ### $ baknow butts
    ### $ baknow butts
    ### cp: overwrite 'butts.2001-12-26_01800000.bak'? n
    ### $ ls -l
    ### total 0
    ### -rw-r--r-- 1 notwa None 0 Dec 25  2001 butts
    ### -rw-r--r-- 1 notwa None 0 Dec 25  2001 butts.2001-12-26_01800000.bak
    ### ```
    ###
    ### **TODO:** support multiple files at once.
    cp -ip "${1:?missing file argument}" "$1.$(now "$1").bak"
}

[ "${SOURCING:-0}" -gt 0 ] || baknow "$@"