Full restore: say to run occ upgrade before rerunning a restore that stopped after the database; remove empty spool folders of a stopped restore

lib/Command/RestoreFull.php

@@ -92,6 +92,7 @@ HELP);
 		} catch (\Throwable $e) {
 			$output->writeln('<error>' . $e->getMessage() . '</error>');
 			$output->writeln('If this happened after the restore had started, the instance may be partly restored: fix the cause and run the same command again with --force.');
+			$output->writeln('If occ then says that Nextcloud needs an upgrade (the database is already the old server\'s), run occ upgrade first.');
 			return 1;
 		}
 		$output->writeln(sprintf(

lib/Repository/Repository.php

@@ -237,6 +237,11 @@ final class Repository {
 		if (!$this->backend instanceof IReadsAhead || !$this->backend->canReadAhead()) {
 			return null;
 		}
+		// what a restore that was stopped left behind: empty, its files were unlinked when opened
+		$stale = glob(rtrim($target, '/') . '/.ngb-restore-spool-*', GLOB_ONLYDIR);
+		foreach ($stale === false ? [] : $stale as $dir) {
+			@rmdir($dir);
+		}
 		$plan = new ReadAheadPlan(rtrim($target, '/') . '/.ngb-restore-spool-' . bin2hex(random_bytes(4)));
 		foreach ($this->streamEntries($snapshotId) as $entry) {
 			if ($prefix !== '' && !str_starts_with($entry['p'], $prefix)) {