I would love to use a chromebook as my main development machine, but the main thing is that I would like to be able to use Git offline. Has anybody moved to a chromebook as their main machine and been able to use version control while not connected to the internet?

One option is to put the Chromebook in dev mode and use Crouton[^1] to install Ubuntu as a chroot. It's easy to do and works well. You can use ChromeOS as usual side by side.

[1]: https://github.com/dnschneid/crouton