Git commit causes data download in partial clone

Hi everyone,

I was recently exploring git partial clone feature because I wanted to contribute to repository which has a lot of binary files. My intent was to only add new files without modifying any existing ones and to download as few data as possible in the process. Here are the steps I followed:

$ git clone --no-checkout --filter=blob:none https://github.com/libretro-thumbnails/Nintendo_-_Nintendo_Entertainment_System.git nes $ cd nes $ echo foo > bar $ git add bar $ git commit bar # causes git fetch behind the scene and download of a lot of objects!

Now for reasons I don't understand the last command cause download of a lot of objects from remote (blobs) which is what I was trying to avoid. By enabling tracing options I can see that it runs fetch operation in the background:

git -c fetch.negotiationAlgorithm=noop fetch origin --no-tags --no-write-fetch-head --recurse-submodules=no --filter=blob:none --stdin

Unfortunately trace doesn't show what refspec is being used for the fetch operation. The regular "git fetch" doesn't cause any additional object downloads.

Is there something I'm doing wrong here or maybe what I'm trying to achieve (contribute to repository without downloading all of its files) is simply not possible?

git version 2.34.1 (Ubuntu 22.04)

Thanks for your time charmocc