I have Xcode installed already, which puts an older version of git in: /usr/local/bin/

Homebrew install newer version of git at: /usr/local/bin/

We have to mannally change $PATH variable to ensure the /user/local/bin comes before /usr/local/bin/

https://github.com/mxcl/homebrew/issues/6432#issuecomment-1624857

By the way, the $PATH environment variable is loaded from this file: /etc/paths