To use your favourite visuall diff-tool with git:
git difftool -t xxdiff HEAD
Or ‘HEAD’ can be any particular file you want to diff.
shows a list of programs it can use… if you happen to have them installed.
There is a thread on stackoverflow that details a few more advanced options, including setting up your own difftool, but I like this one the best, due to its simplicity.
Original post on web.archive.org.