fork from http://d.hatena.ne.jp/dayflower/20090513/1242194477

backup.sh

#!/bin/sh

if [ $# -lt 2 ]; then
    echo "usage: $0 <SOURCE> <DESTINATION>"
    exit 1
fi  

force_trailing_slash() {
    case $1 in
        */) echo -n "$1"    ;;
        *)  echo -n "$1/"   ;;
    esac
}

SRC=`force_trailing_slash $1`
DST=`force_trailing_slash $2`

[ -d "${DST}3" ]      && rm -rf "${DST}3"
[ -d "${DST}2" ]      && mv "${DST}2" "${DST}3"
[ -d "${DST}1" ]      && mv "${DST}1" "${DST}2"
[ -d "${DST}latest" ] && mv "${DST}latest" "${DST}1"

[ -d "${DST}latest" ] || mkdir -p "${DST}latest"

#[ -d "${DST}1" ] && \      # missing --link-dest dir will be ignored
LINK_DEST="--link-dest=../1"


echo "rsync -vvaHz --delete $LINK_DEST ${SRC} ${DST}latest/"
exec rsync -vvaHz --delete $LINK_DEST "${SRC}" "${DST}latest/"