1：原文摘自：http://three20.info/article/2010-10-06-Adding-Three20-To-Your-Project
Introduction
Before you begin using Three20 in your project, you should decide what directory layout works best for you.
Recommended: Shared Layout
In this layout, Three20 is shared between multiple projects. If you need to make project-specific modifications to Three20, use git branches.
If you are unfamiliar with git, it's highly recommended that you learn the basics in order to take advantage of this directory layout.
Directories
Example workflow