t / t4013 / diff.diff-tree_--cc_--shortstat_masteron commit blame: default to HEAD in a bare repo when no start commit is given (a544fb0)
   1$ git diff-tree --cc --shortstat master
   259d314ad6f356dd08601a4cd5e530381da3e3c64
   3 2 files changed, 5 insertions(+)
   4$