--- a/hgext3rd/topic/compat.py	Wed Nov 13 13:43:46 2019 +0700
+++ b/hgext3rd/topic/compat.py	Wed Nov 13 13:47:55 2019 +0700
@@ -10,6 +10,7 @@
 from mercurial import (
     obsolete,
     pycompat,
+    util,
 )
 
 getmarkers = None
@@ -34,3 +35,11 @@
     def branchmapitems(branchmap):
         return branchmap.iteritems()
     # py3-transform: on
+
+# nodemap.get and index.[has_node|rev|get_rev]
+# hg <= 5.3 (02802fa87b74)
+def getgetrev(cl):
+    """Returns index.get_rev or nodemap.get (for pre-5.3 Mercurial)."""
+    if util.safehasattr(cl.index, 'get_rev'):
+        return cl.index.get_rev
+    return cl.nodemap.get