One of the best features of SSDT is deployment contributors. They are so exciting I am going to say it again with more gusto. One of the best features of SSDT is deployment contributors.
What these do is let you examine or modify the deployment script that is generated when SSDT compares a project to a database.
why is that cool? Please imagine for a minute a scenario where you have used SSDT to generate a deployment script and you have looked at it and scoffed that you could have written a better upgrade script.