`rm` command should check for any unpushed commits

[jmalloc]

trafficstars

Equivalent to git log --branches --not --remotes.

• [x] warn about uncommitted changes
• [ ] warn about unpushed commits

[jmalloc]

I'm not really sure how to implement the rest of this. I guess I'll need to iterate over all the local refs (tags and branches) and verify that they exist on at least one of the remotes, or even just origin.