Does Mac OSX Mountain Lion autosave/versions interact badly with git? I use git with some of my documents and wonder if the autosaved versions created by Mountain Lion could interfere (or even break) git versioning? 

This is important for me as I do not work on Macs exclusively. Do I need to edit my .gitignore file to account for the native versioning system in OS X?
Short answer: don't worry about it.

The versions data is kept separate from the file itself, which is why you can just email a file to someone on a different OS and not worry about the version info mucking things up.

Unless you are checking in the hidden folders where OS X stores temporary files and versions, git will never know if a file is being versioned or saved by the OS.