t / t4013 / diff.diff-tree_-c_--stat_--summary_masteron commit t: skip pack tests if not using SHA-1 (2bc3d12)
   1$ git diff-tree -c --stat --summary master
   259d314ad6f356dd08601a4cd5e530381da3e3c64
   3 dir/sub | 2 ++
   4 file0   | 3 +++
   5 2 files changed, 5 insertions(+)
   6$