gitree is a wrapper utility around tree created by Steve Baker et al. It
reads your .gitignore and excludes those paths from being listed in the
output of tree.
If you haven't already, first install Git and Tree. Versions may be available from your package manager (apt-get, homebrew, etc).
Once the dependencies are taken care of, simply copy or link the gitree script file into your PATH.
# Example: copy the script to /usr/local/bin
cp gitree /usr/local/bin