You can't do that, every object is compressed (and then added to pack files with delta-encoding). Even if you did manually write a non-zlib object, things would break the first time Git tried to access that object (for example to show, compare with working copy, gc, or repack).
Thank you, that's very helpful to know! It makes perfect sense, too.
I wonder if I can abuse the pack file format. Mua ha ha. Probably not but learning about Git innards pays dividends even if the experiments don't work out.
