Ejecting should ensure you have clean git status (if you use git) and ask you to commit

[gaearon]

We don't currently integrate with Git, so probably shouldn't commit on your behalf.

But I think we should refuse to eject if you use Git and have dirty Git status.
Right after ejecting, we should also nudge you to commit the change.

This way it's easier to revert an ejection in the future.

Based on conversation with @thejameskyle in https://twitter.com/thejameskyle/status/860133102655602688

[Timer]

#2090