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 just copied an older release of elasticsearch into the /usr/local/Cellar/elasticsearch directory.

$ mkdir /usr/local/Cellar/elasticsearch/5.4.3/bin
$ cp elasticsearch /usr/local/Cellar/elasticsearch/5.4.3/bin
$ brew switch elasticsearch 5.4.3

That's it. Maybe it's useful for anyone.