NetBeans upgrade results in default settings after userdir incompatibility

Symptom

After a NetBeans major version upgrade, the IDE may launch with default settings or fail to start when it detects that the existing userdir is incompatible with the new release.

The upgrade process does not automatically create a backup of the userdir, and there is no built‑in prompt that offers to restore the previous configuration if the new version cannot read it.

Goal: understand whether NetBeans should provide an interactive backup dialog or an automatic rollback mechanism when an upgrade fails due to userdir incompatibility.

• What criteria should trigger an automatic backup prompt during the upgrade?
• How could NetBeans safely roll back to the previous userdir without requiring manual file‑system operations?
• What impact would an automatic backup/restore feature have on upgrade time and disk usage?