So, xz isn't as much of a compression algorithm as a compression container format (which is a big reason why it generates slightly larger files than directly us

So, xz isn't as much of a compression algorithm as a compression container format (which is a big reason why it generates slightly larger files than directly using the lzma tooling, and also the reason why a lot of people dislike it for solving a kind of weird problem); why not just add a filter type for zstd to xz? Adding this support to zstd when we already have this awkward container format to solve this specific problem in isolation seems like the wrong abstraction.