check file existence in archive-push

Author: alubennikova

src/archive.c

@@ -65,6 +65,9 @@ do_archive_push(char *wal_file_path, char *wal_file_name)
 	join_path_components(absolute_wal_file_path, current_dir, wal_file_path);
 	join_path_components(backup_wal_file_path, arclog_path, wal_file_name);
 
+	if (access(absolute_wal_file_path, F_OK) != -1)
+		elog(ERROR, "file '%s', already exists.", absolute_wal_file_path);
+
 	elog(INFO, "pg_probackup archive-push from %s to %s", absolute_wal_file_path, backup_wal_file_path);
 	copy_wal_file(absolute_wal_file_path, backup_wal_file_path);
 	elog(INFO, "pg_probackup archive-push completed successfully");