Question: Getting 'git diff' to generate /usr/bin/diff output

I am trying to learn how to use git, and am having difficulty using 'git diff'.

I can't deal with its output very well. What I would really like to do is apply /usr/lib/diff. Would some kind soul be willing to tell me if there is a way to do that, short of making a backup copy of the relevant file, and then doing 'git checkout'. Maybe the '--ext-diff' argument to 'git diff' will do that, but I can't figure out how to use it.

Thank you, most kindly.

Context:

    Operating System: Red Hat Enterprise Linux Workstation release 6.8

    git version: 2.5.1.454.g1616360

 Norman Shapiro