[Feature Request] Optimise backup strategy

[zvecr]

Description

Right now its just tar of the entire home directory, though it would be good to...

• use partial updates
  • rsync
• ignore as much as possible
  • only qmk_firmware?
• as fast as possible on uninstall
  • rsync if done at least once
  • tar otherwise?
• configurable target directory?

[zvecr]

Current Status

• Implemented basic backup and restore menu within qmk-admin
• Validated rsync is too slow for use on raw files
  • > 4 mins rsync vs 20s for zx + rsync
  • main slowdown seems to be in the amount of size and timestamp calls for a clone of qmk_firmware
• Backup only copied if different
• "Hidden" option for setting backup destination

Next steps?

• Restore backup on upgrade
• Validate use of /tmp as tmpfs
• Conf file for which folders to backup?
• get QMK_HOME when not set