Possible bug with multiple mv's and diff output

Hi all,

When I do this in repo with files a and b:
  git mv b c
  git mv a b
  git commit -m shuffle
  git diff --summary master^ master

I get output:
  delete mode 100644 a
  create mode 100644 c
Which does not indicate that the contents of b changed.

  git diff --summary --find-copies --find-renames master^ master
gives output
  delete mode 100644 a
  copy b => c (100%)
which also doesn't show that b changed.

"git diff --raw" shows more complete information.

I am misunderstanding what should happen, or is this incorrect?

Thanks,
Kent Leonard