Something

#!/bin/bash

# kill existing processes.. adjust this if necessary
killall xulrunner

if [ -d /Applications/Vesta_bak.app ]
then
    rm -fr /Applications/Vesta_bak.app
fi

if [ -d /Applications/Vesta.app ]
then
    mv /Applications/Vesta.app /Applications/Vesta_bak.app
fi

# change BuildID:
perl -p -i -e "s/BuildID=([0-9]+)/BuildID=`date '+%Y%m%d%H%M'`/" Vesta/application.ini

# install it:
/Library/Frameworks/XUL.framework/xulrunner-bin --install-app Vesta/

echo "Vesta installed: /Applications/Vesta.app"