Iterator work overview

Bugs

• #158
  • Only impacts certain environments.

Suspected to be same root cause:

The below are likely related to #158 (which can be confirmed once a solution is developed).

• core/shipped.json disappearing from prior updates leading to failures on the next update
  • #131
  • #222
  • #434
• Other previously mysterious deleteOldFiles() situations
  • #249
• Likely some of the previously mysterious createBackup() situations
  • https://github.com/nextcloud/updater/issues?q=is%3Aopen+is%3Aissue+label%3A%22feature%3A+backups%22

Fixes/PRs:

• #515 targeting #158
  • Note: reverted in #518 due to #517
  • a new solution is required 😞

Enhancements

• #507
• #397

The above are performance matters that impact all environments. The solution required for both of the above will in all likelihood be the same.

Fixes/PRs:

• #516 (WIP/draft)

Cc: @caco3, @Altahrim, @blizzz, @kesselb, @come-nc