git-diff-tree --root

hello,

git-diff-tree without --root is absolutely silent for the root commit,
and i see no bad effects of --root on non-root commits.  are there any
hidden gotchas?  IOW, why is the --root behavior not the default?

cram[1] testcase::

  $ git init -q scratch
  $ cd scratch
  $ echo '.*.sw?' > .gitignore
  $ git add .gitignore
  $ git commit -q -m init .gitignore

  $ git diff-tree HEAD

  $ git diff-tree --root HEAD
  [0-9a-z]{40} (re)
  :000000 100644 0000000000000000000000000000000000000000 [0-9a-z]{40} A\\t.* (re)

[1] https://pypi.python.org/pypi/cram

-- 
roman