Homebrew is a great little package manager for OS X. If you haven't already, installing it is pretty easy:
ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"
o you've contributed some code to an open source project, say, Rails. And they'd like you to squash all of the commits in your pull request. But you're not a git wizard; how do you make this happen?
Normally, you'd do something like this. I'm assuming upstream is a git remote that is pointing at the official project repository, and that your changes are in your 'omgpull' branch: