git clean -fdx deletes tracked files

Hi

I hope this is gonna sound as weird to you as it does to me.

The link below is a zip of a small git repository that I can reproduce the bug in on 2 machines.

Repo: https://www.dropbox.com/s/fz4d0i5ko7s7ktr/test.zip?dl=0

It contains 2 folders: helpers and b, each of which is an empty npm module. b\package.json refers to the helpers module.

The following reproduces the bug:

1) in terminal cd to the b folder
2) run npm install
3) run git reset HEAD --hard
4) run git clean -fdx

At this point both files in the helpers folder has been deleted and running git status confirms this.

Tool version:

git --version => git version 2.10.2.windows.1 node -v => v6.11.2 npm -v => 5.3.0

I have no idea what is going. Very much hope you can explain :-)