Empty folders in backup and restore, a full disk stops a restore, progress in the Bin

- Record folders without files in the meta record of a snapshot and restore them (#27)
- Errors writing to the restore directory stop the restore, also with --salvage
- Resume: check the folder before skipping, clean temporaries in folders that are complete
- Clean only read-ahead folders of our own; refresh the lease on skipped files
- Drop tables a failed database restore created; keep --salvage from calling a restored database fresh
- Retry a pack that fails to open on the storage (SMB)
- Without cron, running backups take turns from the open page
- Bin: read in parts with a counter and progress bar, show read errors, refresh when a run ends

lib/Service/RestoreFullService.php

@@ -175,6 +175,8 @@ final class RestoreFullService {
 			if ($dbError === null) {
 				try {
 					$this->restoreDatabase($repo, $meta, $manifest, $dbReport, $beat, $skipMissingTables);
+				} catch (DatabaseAlreadyRestoredException $e) {
+					throw $e;
 				} catch (\Throwable $e) {
 					if (!$salvage) {
 						throw $e;
@@ -259,8 +261,20 @@ final class RestoreFullService {
 		$dumper = new DbDumper($this->db->getInner(), $prefix);
 		try {
 			$dumper->restore($repo, $manifest, $dbReport, $beat, $skipMissingTables);
-		} finally {
+		} catch (\Throwable $e) {
+			try {
+				$this->restoreOwnAppConfig($ownAppConfig);
+			} catch (\Throwable) {
+				// rolled back, so they are still there: the error that brought us here is the one to report
+			}
+			throw $e;
+		}
+		try {
 			$this->restoreOwnAppConfig($ownAppConfig);
+		} catch (\Throwable $e) {
+			// The old server's database is in place by now: not a case for "the database stays as
+			// the fresh installation made it" under --salvage. A run again restores these rows.
+			throw new DatabaseAlreadyRestoredException('The database was restored, but NG Backup could not put back its own settings: ' . $e->getMessage(), 0, $e);
 		}
 	}