[DRAFT] Switch distribution sets to tzst (tar+zstd)

[emaste]

Summary

Not yet tested (beyond make packageworld); posting for reference & discussion

[emaste]

Tested installation with a disc1.iso built with this change in a VM.

[delphij]

Do we have data about how much difference in size would this cause? (for example, is DVD / cost for network bandwidth still a concern, or do we still have plenty of grow space? And should we use a higher compression level for zstd? The default for zstd was 3, IIRC, decompression speed / memory requirement won't increase so much until level 9, while compression ratio would be significantly better than default for highly compressible data).

[emaste]

In D48042#1095840, @delphij wrote:

Do we have data about how much difference in size would this cause? (for example, is DVD / cost for network bandwidth still a concern, or do we still have plenty of grow space? And should we use a higher compression level for zstd? The default for zstd was 3, IIRC, decompression speed / memory requirement won't increase so much until level 9, while compression ratio would be significantly better than default for highly compressible data).

Yeah, we would likely want to use a higher compression level. I don't have size/speed comparisons handy but would definitely need them before any decision to proceed with this.

Responses to my thread on -current all expressed a preference for better compression at the cost of compression & decompression time. Given that these are compressed once per release, and are decompressed once per install of that release that seems reasonable.