t / t5100 / info0010on commit pre-commit.sample: Diff against the empty tree when HEAD is invalid (c30eb85)
   1Author: Lukas Sandström
   2Email: lukass@etek.chalmers.se
   3Subject: git-mailinfo: Fix getting the subject from the body
   4Date: Thu, 10 Jul 2008 23:41:33 +0200
   5