compare parent backup version with current binary version while searching for valid ancestor

Author: kuzmindb

src/backup.c

@@ -218,6 +218,12 @@ do_backup_instance(PGconn *backup_conn, PGNodeInfo *nodeInfo, bool no_sync)
 
 	if (prev_backup)
 	{
+        if (parse_program_version(prev_backup->program_version) > parse_program_version(PROGRAM_VERSION))
+            elog(ERROR, "pg_probackup binary version is %s, but backup %s version is %s. "
+                        "pg_probackup do not guarantee to be forward compatible. "
+                        "Please upgrade pg_probackup binary.",
+                        PROGRAM_VERSION, base36enc(prev_backup->start_time), prev_backup->program_version);
+
 		char		prev_backup_filelist_path[MAXPGPATH];
 
 		elog(INFO, "Parent backup: %s", base36enc(prev_backup->start_time));