The symlinks taps write to Formula show up in git status, but this trick prevents this. brew-(un)tap maintain a .gitignore in Formula that contains all the symlinks brew-tap creates.
We add the .gitignore to the root .gitignore and TADA! Magic.
Will be useful for a variety of reasons, but for now, I'm just using it to ensure install won't install again if something is already installed (use brew upgrade instead).
But means that brew switch and that can work properly etc.
Moved Forumla and Cellar/homebrew into Library.
This way the homebrew core files are more sensibly placed, Cellar is
more internally consistent and only generated. And Homebrew is ready for
use straight out of the tarball.