This refers to Git 2.0, that will bring breaking changes, like the default push mode. I don't know any other source than the weekly "what's cooking in Git" post

This refers to Git 2.0, that will bring breaking changes, like the default push mode. I don't know any other source than the weekly "what's cooking in Git" posts by Git maintainer on the mailing list, but it's fairly hard to read if you're not used to Git internals.