Can't run git diff --dirstat=files,10,cumulative HEAD^..HEAD

I want to know change status of directory with percentage. So I run like following

case 1

$ git diff --dirstat=files,10,cumulative HEAD^..HEAD
usage: git diff [<options>] [<commit> [<commit>]] [--] [<path>...]

case 2

$ git diff --dirstat=11 HEAD^..HEAD
  76.8% api/
  13.0% data/fonts/

I have tested this under git 1.7.5.4 and 1.7.0.4. But I don't know why case 1 is not correct command. I checked git diff man page http://goo.gl/GPU49 also git config for diff.dirstat but I can't do it correctly.

Do you have any opinion?

Solution

I tested it in my mac and linux server with git version 1.7.6 then there had no problem. But when I tried it in my mac and linux server with git version 1.7.5.4, there had same problem.

# git version 1.7.5.4
$ git diff --dirstat=10,lines,cumulative  HEAD^^^^^^^..HEAD
usage: git diff [<options>] [<commit> [<commit>]] [--] [<path>...]

# git version 1.7.6
$ git diff --dirstat=10,lines,cumulative  HEAD^^^^^^^..HEAD
  17.7% core/
  41.9% tools/releasetools/

I can't find this fix in git 1.7.6 release note. http://www.kernel.org/pub/software/scm/git/docs/RelNotes/1.7.6.txt Anyway it's OK in git 1.7.6.