zodbinfo: Provide "head" as command to query DB head; Turn "last_tid" into...

zodbinfo: Provide "head" as command to query DB head; Turn "last_tid" into deprecated alias for head

Similarly to go version: kirr/neo@151d8b79.

zodbtools/zodbinfo.py

 # -*- coding: utf-8 -*-
-# Copyright (C) 2017  Nexedi SA and Contributors.
+# Copyright (C) 2017-2020  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -25,11 +25,16 @@ from collections import OrderedDict
 from golang import func, defer
 import sys
 
+def _last_tid(stor):
+    print("W: last_tid is deprecated alias for head", file=sys.stderr)
+    return infoDict["head"](stor)
+
 # {} parameter_name -> get_parameter(stor)
 infoDict = OrderedDict([
     ("name", lambda stor: stor.getName()),
     ("size", lambda stor: stor.getSize()),
-    ("last_tid", lambda stor: ashex(stor.lastTransaction())),
+    ("head", lambda stor: ashex(stor.lastTransaction())),
+    ("last_tid", _last_tid),
 ])
 
 def zodbinfo(stor, parameterv):