--- a/hgext3rd/evolve/stablerange.py	Sat Dec 09 22:49:07 2017 +0100
+++ b/hgext3rd/evolve/stablerange.py	Sun Dec 10 00:20:06 2017 +0100
@@ -570,7 +570,6 @@
 
     def _slicesrangeatmerge(self, repo, rangeid, globalindex):
         localindex = globalindex - rangeid[1]
-        cl = repo.changelog
 
         result = []
         allrevs = self.revsfromrange(repo, rangeid)
@@ -581,19 +580,24 @@
             # revision we needs
             result.append((bottomrevs[-1], rangeid[1]))
         else:
-            parentrevs = cl.parentrevs
-            parents = self._parents
-            bheads = set(bottomrevs)
-            du = bheads.difference_update
-            for r in bottomrevs:
-                du(parents(r, parentrevs))
-            seen = 0
-            for r in bottomrevs:
-                seen += 1
-                # XXX bheads might not be a good enough criteria
-                if r in bheads:
-                    result.append((r, self.depthrev(repo, r) - seen))
-                    seen = 0
+            head = None
+            headrange = None
+            skip = None
+            for rev in bottomrevs[::-1]:
+                if head is None:
+                    head = rev
+                    headrange = self.revsfromrange(repo, (head, 0))
+                    skip = self.depthrev(repo, rev) - 1
+                elif rev != headrange[skip - 1]:
+                    result.append((head, skip))
+                    head = rev
+                    headrange = self.revsfromrange(repo, (head, 0))
+                    skip = self.depthrev(repo, rev) - 1
+                else:
+                    skip -= 1
+            result.append((head, skip))
+
+            result.reverse()
 
         # top part is trivial
         top = (rangeid[0], globalindex)