Homebrew recently added bottles for Vim/MacVim — but they depend on Homebrew-installed Ruby, Python, and Perl. I prefer to build these from source so they will use whatever versions of these dependencies currently installed on my system. Instead of constantly remembering brew install -s vim to install from source, I created a couple small formulae that disable bottles.

For Vim:

require "#{HOMEBREW_PREFIX}/Library/Formula/vim"

Vim.bottle :disable

For MacVim:

require "#{HOMEBREW_PREFIX}/Library/Formula/macvim"

Macvim.bottle :disable

Install with brew install itspriddle/brews/vim and brew install itspriddle/brews/macvim to compile from source. Upgrade with brew upgrade vim or brew upgrade macvim and upgrades will compile from source as well.

I haven’t tried anything beyond disabling bottles, but this technique could be useful to override any Homebrew formula.