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

Install an old brew package version (Flyway 4.2.0 example)

Find your local homebrew git dir or clone Homebrew/homebrew-core locally

cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/

OR

git clone git@github.com:Homebrew/homebrew-core.git

List all available versions

git log master -- Formula/flyway.rb

Copy the commit ID for the version you want and install it directly

brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/793abfa325531415184e1549836c982b39e89299/Formula/flyway.rb