--- a/mercurial/revlog.py	Sat Nov 09 05:54:22 2019 +0100
+++ b/mercurial/revlog.py	Sun Nov 03 00:01:09 2019 +0100
@@ -213,6 +213,10 @@
             nodemap[n] = r
         return nodemap
 
+    def has_node(self, node):
+        """return True if the node exist in the index"""
+        return node in self.nodemap
+
     def append(self, tup):
         self.nodemap[tup[7]] = len(self)
         super(revlogoldindex, self).append(tup)