Disable incremental backups with ptrack 1.X, as it is unsafe.

Instead of throwing an error, throw a warning and fall back to performing DELTA backup, as we don't want to break existing scripts.

Author: alubennikova

src/ptrack.c

@@ -202,9 +202,21 @@ get_ptrack_version(PGconn *backup_conn, PGNodeInfo *nodeInfo)
 	else if (strcmp(ptrack_version_str, "2.1") == 0)
 		nodeInfo->ptrack_version_num = 21;
 	else
-		elog(WARNING, "Update your ptrack to the version 1.5 or upper. Current version is %s",
+		elog(WARNING, "Update your ptrack to the version 2.1 or upper. Current version is %s",
 			 ptrack_version_str);
 
+	/* ptrack 1.X is buggy, so fall back to DELTA backup strategy for safety */
+	if (nodeInfo->ptrack_version_num >= 15 && nodeInfo->ptrack_version_num < 20)
+	{
+		if (current.backup_mode == BACKUP_MODE_DIFF_PTRACK)
+		{
+			elog(WARNING, "Update your ptrack to the version 2.1 or upper. Current version is %s. "
+						"Fall back to DELTA backup.",
+				ptrack_version_str);
+			current.backup_mode = BACKUP_MODE_DIFF_DELTA;
+		}
+	}
+
 	PQclear(res_db);
 }