[Feature Request] zsync adoption for AppImage updates

[davidhedlund]

zsync is becoming increasingly popular for distributing AppImage updates. For instance, current releases of PPSSPP, Ryujinx (Ryubing), and Vita3K all provide zsync support.

From libretro/docs#1135 (comment)

Given the size of the packages, it would be even easier to update them if they were redistributed outside of the 7z archive that contains them, and with the necessary information for delta updates.

I wrote a guide to implement this information and make AppImages faster to update using appimageupdatetool and zsync. It is just 5 minutes reading:

https://github.com/ivan-hc/AppImage-tips

I'm the maintainer of AM. Thanks @davidhedlund for the support.

AppImages

• https://buildbot.libretro.com/nightly/linux/x86/RetroArch.7z
• https://buildbot.libretro.com/nightly/linux/x86/RetroArch_Qt.7z
• https://buildbot.libretro.com/nightly/linux/x86_64/RetroArch.7z
• https://buildbot.libretro.com/nightly/linux/x86_64/RetroArch_Qt.7z
• https://buildbot.libretro.com/stable/1.22.2/linux/x86/RetroArch.7z
• https://buildbot.libretro.com/stable/1.22.2/linux/x86/RetroArch_Qt.7z
• https://buildbot.libretro.com/stable/1.22.2/linux/x86_64/RetroArch.7z
• https://buildbot.libretro.com/stable/1.22.2/linux/x86_64/RetroArch_Qt.7z

Needed zsync files

• https://buildbot.libretro.com/nightly/linux/x86/RetroArch.7z.zsync
• https://buildbot.libretro.com/nightly/linux/x86/RetroArch_Qt.7z.zsync
• https://buildbot.libretro.com/nightly/linux/x86_64/RetroArch.7z.zsync
• https://buildbot.libretro.com/nightly/linux/x86_64/RetroArch_Qt.7z.zsync
• https://buildbot.libretro.com/stable/1.22.2/linux/x86/RetroArch.7z.zsync
• https://buildbot.libretro.com/stable/1.22.2/linux/x86/RetroArch_Qt.7z.zsync
• https://buildbot.libretro.com/stable/1.22.2/linux/x86_64/RetroArch.7z.zsync
• https://buildbot.libretro.com/stable/1.22.2/linux/x86_64/RetroArch_Qt.7z.zsync