Large git repositories cause noticeable lag in shell

[ryanaddams]

When you are moving about in a large git repo, creating the git prompt can be extremely slow, e.g., it can take 5 seconds or more to change directories within the folder structure, using any shell commands, etc., due to the method that bashrc uses to get and display git information for the repository. This should be cached or an alternative/simpler method for retrieving the information utilized.