Negative patterns in cone mode

Hi all,

I'm facing an issue with negative patterns in cone mode. I can't tell from the docs or git code if I misunderstand the usage, am trying something not supported, or if there is a bug.

What I want to do is exclude a small number of directories (and their subdirectories) from a large repo, without explicitly declaring all the other directories that I wish to keep.

My directory structure is:
root
^----A
        ^----B
        ^----C

My sparse-checkout file is: /* !/A/B/

I've set up an MRE:
1. git clone --sparse https://github.com/peakschris/sparse.git
2. cd sparse
3. copy sparse-checkout.txt .git\info\sparse-checkout
4. git sparse-checkout reapply

Output: git sparse-checkout reapply warning: unrecognized negative pattern: '/A/B' warning: disabling cone pattern matching warning: unrecognized negative pattern: '/A/B' warning: disabling cone pattern matching

Thanks! Chris