Make RC backup command cwd independent

backend/tests/test_rc_backup_restore_scripts.py

@@ -20,6 +20,8 @@ def test_backup_is_atomic_read_only_and_checksum_bound() -> None:
     assert "--no-owner" in script
     assert "CHECKSUMS.sha256" in script
     assert "database-password" not in script.lower()
+    assert 'git -C "$ROOT" rev-parse HEAD' in script
+    assert 'git -C "$ROOT" status --porcelain=v1' in script
     assert "mv \"$PARTIAL\" \"$FINAL\"" in script
     assert "rm -rf -- \"$PARTIAL\"" in script
     assert "DROP DATABASE" not in script