Side note: why are shallow clones evil? I always thought they were cheaper, but I guess that’s really just for my disk space. (since the server has to compute what blobs to give you instead of just “everything”?)
Normal clones can reuse delta-compressed data the server stored on disk. Shallow clones impose a negative constraint: do not transfer data outside the requested commit depth. Pre-computed delta chains than contain unrequested data become unusable and the server must do delta compression on the fly to satsify the shallow clone.