Backing up my DokuWiki with Tarsnap

My DokuWiki is backed up nightly using this script, excluding ever-changing directories:

#!/bin/sh
/home/username/tarsnap/inst/bin/tarsnap -c \
        -f "username-$(date +%Y-%m-%d_%H-%M-%S)" \
        --exclude cache \
        --exclude index \
        --exclude locks \
        --exclude tmp \
        /var/www/virtual/username/html/data \
        /var/www/virtual/username/html/conf

And then call it from crontab.