diff – Wikipedia
http://ja.wikipedia.org/wiki/Diff#.E3.83.A6.E3.83.8B.E3.83.95.E3.82.A1.E3.82.A4.E3.83.89.E5.BD.A2.E5.BC.8F_.28Unified_format.29

diff & patch コマンドでのパッチを適用する方法 – hogehoge foobar Blog Style5
http://d.hatena.ne.jp/mrgoofy33/20101019/1287500809

The Ten Minute Guide to diff and patch
http://jungels.net/articles/diff-patch-ten-minutes.html