A announcement has just been made a a severe critical vulnerability in git. After trying to update my git from 2.1.0 to 2.2.1 with Homebrew, I realised I was getting nowhere.
brew upgrade git was reporting 2.1.0 as the correct version. The error? I needed to update homebrew as well. Here are the two commands you will need:
brew upgrade git
You can then check which version of git you have by inputting git --version
markconroy$ git --version
git version 2.2.1