WordPress has just announced official git mirrors for WordPress . These are read-only mirrors for WordPress core development SVN repository. Git mirrors are also available for bbPress, BuddyPress,GloPress and the core.svn build repository.
The contribution process is not as direct but there is a tutorial on how to contribute to WordPress using GitHub. In the future, WordPress will also be making git mirrors for WordPress plugins and themes.
For the next week, it will be in beta so expect a few bugs. This new git mirror opens up to an even greater improvement especially in the enhancements and fixes of WordPress.
Read the rest of the post here: http://wptavern.com/official-git-mirror-now-available-for-wordpress-core-development-repository