This is how I use two remotes "origin" and "samuel" and have the master branch use origin so `brew update` works as usual. When I want to contribute, I use: `git checkout -b my_new_feature` and then `git push --set-upstream samuel my_new_feature` to push it to my own fork ("samuel") of homebrew.

config

[core]
  repositoryformatversion = 0
	filemode = true
	bare = false
	logallrefupdates = true
	ignorecase = true
	autocrlf = false
[color]
	branch = auto
	status = auto
	interactive = auto
	diff = auto
[prompt]
	showinfo = true

[remote "samuel"]
	fetch = +refs/heads/*:refs/remotes/samuel/*
	url = git@github.com:samueljohn/homebrew.git
[remote "origin"]
	url = https://github.com/mxcl/homebrew.git
	fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
	remote = origin
	merge = refs/heads/master