Add the "jgit diff" command

This commit contains fixes provided by Christian Halstrick.

Bug: 291083
Eclipse-CQ: 3559
Change-Id: If8d187e70a51f31040f99098489e513791dc6415
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
3 files changed