Add an opt-in (off by default) toggle to include app data in system
Android Backup / Auto Backup, gated so only re-creatable user
preferences are ever backed up.
- Flip allowBackup to true and add LibreMailBackupAgent, which enforces
the runtime opt-in: onFullBackup runs only when the user enables
"Include settings in Android Backup" (default off), so no data leaves
the device otherwise. allowBackup is a manifest flag and can't be
toggled at runtime, hence the agent.
- Rewrite data_extraction_rules.xml (API 31+) and add backup_rules.xml
(API 29-30) as strict allowlists that back up ONLY the
libremail_settings DataStore. The Keystore-sealed cache passphrase
(libremail_dbkey) and the encrypted credentials + mail-cache database
(libremail.db) are excluded by omission; the cache re-downloads on
next sync.
- Add includeInBackup preference + setter (nudges BackupManager on
change) and a "Backup" settings section with F-Droid-honest copy
(off by default, uses Google infrastructure).
- BackupPolicy is the single source of truth for eligible/excluded
paths; unit tests cover the toggle default and assert the shipped XML
resources include only settings and never the secrets/DB.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
JMR-dev
