Use kdiff3 as your diff viewer in git.
Copy git-kdiff3
somewhere into your $PATH
or your git exec path
(usually /usr/libexec/git-core/):
sudo cp git-kdiff3 "`git --exec-path`"
Compare working copy against HEAD
:
git kdiff3
Compare working copy against a specific commit/branch:
git kdiff3 $branch
Compare two commits:
git kdiff3 $commit1 $commit2