When a clone gets reset (git reset --hard origin/main), the
git-history-backfill logic was incorrectly marking ALL issues as
deleted since they appeared in git history but not in the current
JSONL. This caused the entire database to be purged.
Fix:
- Add 50% threshold check: abort if git-history-backfill would delete
more than 50% of issues (likely a reset scenario, not deletions)
- Add warning when >10 issues would be deleted via backfill
- Print helpful message about manual deletion if needed
Test:
- Added TestMassDeletionSafetyGuard that simulates JSONL reset and
verifies the safety guard prevents mass deletion
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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