Show git diff information in fringe.  You can use this package
only with GUI Emacs, not in a terminal Emacs.

To use this package, add following code to your init.el or .emacs

(require 'git-gutter-fringe)
(global-git-gutter-mode t)

; If you want to show git diff information at right fringe
(setq git-gutter-fr:side 'right-fringe)