I would argue it's not even that difficult. In the README.md, put some kind of note that there's a bug in the current version of git (and maybe point to some random Google group posting) and mention that on OS X it's better to use the XCode version.
This is indeed an issue. I would like to think that a person capable of using git would have enough of a critical mindset not to do what random people on the internet tell you to do, but... StackOverflow kinda proves the opposite.
I don't think you'll ever be able to help people that follow internet advice blindly, for these people, it might be better not to bundle anything at all.
