cc @dalias i'm also recalling your patient feedback a few weeks ago about compression and this is absolutely validating your assertion that compression is often inappropriate particularly on something like a filesystem. i think it's a fun problem but i absolutely hesitate to involve it in a system where integrity is a concern
@dalias google apparently modified the go language's DEFLATE algorithm recently, which will modify checksums (???) and while zip files can be made to retain per-file checksums, by default they only store CRCs. i don't think compression should ever be nondeterministic but it's given me pause about incorporating it elsewhere