This is a script that calculates the average age of your code lines using git blame and math.
Clone this repo somewhere on your computer:
git clone git@github.com:draperunner/code-age.git
Create a symbolic link to the code-age.sh to some bin folder that's on your path.
cd /usr/local/bin
ln -s /path/to/projects/code-age/code-age.sh code-age
Now you can run code-age anywhere you'd like. Keep it updated by running git pull in the repo.