gitstat: Add an option to only stat the files diff
gitstat: Add an option to only stat the files diff

 * Smaller result for mass comparing, example:

 Project CyanogenMod/android_packages_apps_CMUpdater [...]
  src/com/cyanogenmod/updater/UpdatesSettings.java | 6 ++++++
  1 file changed, 6 insertions(+)

Change-Id: I71cca4d792f66b002533917a5383e38393c6f993
Signed-off-by: Adrian DC <01fb3892f39957945220431e7409156544d2f041@gmail.com>

AdrianDC/android_development_shell_tools,AdrianDC/android_development_shell_tools