Lots of good stuff here. I would appreciate a wiki-style site with short answers like these instead of searching {Google,DDG} and trawling the [stackoverflow] results. Not all of them are necessarily good practice though. This made me chuckle: What Is The Current [Git] Branch? git rev-parse --abbrev-ref HEAD (if you're reading this jbranchaud, try `git branch` :p)
`git rev-parse --abbrev-ref HEAD` is very inexpensive in comparison, and doesn't print anything extra you might need to parse out if you're in a shell script.