Homebrew install specific version of formula?

Question

How do I install a specific version of a formula in homebrew? For example, postgresql-8.4.4 instead of the latest 9.0.

Answer 1

I've tried most of the solutions here and they are outdated. I had to combine some ideas from here with my own work. As a result I've created a script to help me do the heavy lifting which you can find here

Usage:

brewv.sh formula_name desired_version