#!/bin/sh

# prepends date to the filename unless it already exists.
# path -> dirname/yyyy-mm-dd.basename

date=$(date +%Y-%m-%d)

for a in "$@"
do
  base="$(basename "$a")"
  date_regexp='^[0-9]{4}-[0-9]{2}-[0-9]{2}'
  if ! echo "$base" | grep -E "$date_regexp" > /dev/null
  then
     dir="$(dirname "$a")"
     mv "$a" "$dir/$date.$base"
  fi
done