Proposal: Compress releases using xz instead of gzip

[randombit]

It seems like these days xz is quite common, my understanding it is built into macOS Finder now, 7-Zip supports it, and of course it works on Linux/Unix. It also saves quite a bit of space, reducing the release file by about 1.5 MiB:

Format	Size	%gzip
gzip	7246839	100%
bzip2	6376353	88%
xz	5547524	76%

I'm going to add a notice to the 2.10 changelog and advertise the change on the mailing list. If no objections are raised then 2.11 onwards will be compressed with xz instead of gzip.

[jimcruse]

I understand that zpaq and kgb than xz

[randombit]

Balancing compression ratio and wide-spread availability, xz seems best. For instance afaik neither zpaq nor kgb are supported by macOS Finder. It's nice to save space but making someone install a special tool they wouldn't otherwise use just to decompress a release adds a lot of friction.

[bkircher]

As far as Fedora packaging is concerned this is fine.