--- a/hgext3rd/evolve/stablerange.py	Wed Dec 20 19:47:19 2017 +0100
+++ b/hgext3rd/evolve/stablerange.py	Wed Dec 20 20:17:11 2017 +0100
@@ -460,17 +460,6 @@
         assert 0 < skips, skips
         assert 0 < tomap, (tomap, (headrev, initial_index), slicepoint)
 
-        # utility function know the size of segment
-        # (this value could be cached)
-        def until(start, stop):
-            revs = walkfrom(start)
-            count = 0
-            for count, r in enumerate(revs, 1):
-                if r == stop:
-                    break
-            assert 0 < count, (start, stop)
-            return count
-
         # utility function to find the next changeset with jump information
         # (and the distance to it)
         def nextmerge(startrev):