I jut would like to share my experience by using Bitbucket.org. I really recommend that for all developers who developing themes. The best important part it provide member collaboration in coding, also it supports versioning and all that are free and it’s private (for limited number of members). One important feature that we have tested and like it very much. The Auto-deploy option to our production server. we can update our codes on our production server from bitbucket or even from our local servers.
Read this tutorial to guide you, Thanks to jonathan for his tutorial