GFDRR Open Source Mentoring Guide
Using a source code management system is absolutely required in any modern development project. If you have never used git and are not familiar with github, you should follow the all of the material below. If you have used other version control tools, but are not yet familiar with git, you should still follow these sections. Your mentor can help you test against a repo you create to help you understand concepts about pulling, merging and branching.