Stranges with git-diff-index

Hi,

I've found this strange thing in git diff-index. I've got a clear work tree (all changes are commited). Then I've changed some files. After this I've run `git diff-index --name-status HEAD` and this command showed me changed files. After this I've undid this changes (I did this myself, not using git-reset or any stuff like this). But when I run this command again it showed me that this files are still changed. After this I've run git-status and it told me that there is nothing to commit. And after this git-diff-index tells me that there is no changed files too.

I think it's not normal.