this is from http://news.ycombinator.com/item?id=429573

#-------- ~/backup.command -----------

# Backup up home dir using git. Note the full path to git (needed for cron jobs):
cd ~/
/opt/local/bin/git add . 
/opt/local/bin/git commit -a -m "home dir backup"
/opt/local/bin/git pull
/opt/local/bin/git push

# Backup binary stuff using rsync
rsync -Cauvzd  /Users/Shared/Music/ user@server:/var/backups/music
rsync -Cauvzd  /Users/Shared/Photos/ user@server:/var/backups/photos

---

so the plan would be to clone the dropbox

git clone mydropbox@hawk:/home/mydropbox/var/MyDropBox.git

and copy over the sync script

scp mydropbox@hawk:/home/mydropbox/bin/sync-MyDropBox.sh .

and then run it in a cronjob…

SHELL=/bin/bash
PATH=/sbin:/usr/sbin:/usr/local/sbin:/bin:/usr/bin
MAILTO=mark.mims@agiledynamics.com
HOME=/home/mmm

# m h  dom mon dow   command

*/10 * * * *  $HOME/bin/sync-MyDropBox.sh

---

the sync script looks like

#!/bin/bash

MY_DROP_BOX=${HOME}/MyDropBox
MY_DROP_BOX_SERVER="mydropbox@hawk:/home/mydropbox/"
GIT=/usr/bin/git
RSYNC=/usr/bin/rsync

if [ -d $MY_DROP_BOX ]
then
  cd $MY_DROP_BOX
  $GIT add .
  $GIT commit -a -m'MyDropBox sync'
  $GIT pull
  $GIT push
fi

for directory in Downloads Music Photos Videos
do
  rsync -Cauvzd ${MY_DROP_BOX}/${directory} ${MY_DROP_BOX_SERVER}var/binary-data/${directory}
done