Inconsistency in specifying commit & path for git diff

git diff <commit>..<commit>
and
git diff <commit> <commit>
both succeed

however
git diff <commit>:<path>..<commit>:<path>
fails while
git diff <commit>:<path> <commit>:<path>
succeeds

OS X 10.7.5
git version 1.7.9.1

Reproduced by another user:
http://stackoverflow.com/questions/12805004/git-cherry-pick-creates-blobs-not-commits#comment17319876_12805004

It seems logical to support the '..' syntax in both for consistency.