--- a/mercurial/revlog.py	Mon Jul 16 14:15:29 2018 -0400
+++ b/mercurial/revlog.py	Fri Jul 20 11:17:33 2018 -0700
@@ -1070,12 +1070,15 @@
     def revs(self, start=0, stop=None):
         """iterate over all rev in this revlog (from start to stop)"""
         step = 1
+        length = len(self)
         if stop is not None:
             if start > stop:
                 step = -1
             stop += step
+            if stop > length:
+                stop = length
         else:
-            stop = len(self)
+            stop = length
         return xrange(start, stop, step)
 
     @util.propertycache