diff -r 4a81d82474e9 -r f1a39128da95 mercurial/repository.py
--- a/mercurial/repository.py	Sun Oct 21 22:26:00 2018 -0400
+++ b/mercurial/repository.py	Wed Oct 03 14:57:29 2018 -0700
@@ -484,6 +484,16 @@
     def __iter__():
         """Iterate over revision numbers for this file."""
 
+    def hasnode(node):
+        """Returns a bool indicating if a node is known to this store.
+
+        Implementations must only return True for full, binary node values:
+        hex nodes, revision numbers, and partial node matches must be
+        rejected.
+
+        The null node is never present.
+        """
+
     def revs(start=0, stop=None):
         """Iterate over revision numbers for this file, with control."""