diff -r f0933cdf614d -r fd90e73bf79a hgext3rd/evolve/utility.py
--- a/hgext3rd/evolve/utility.py	Thu Dec 21 00:06:07 2017 +0100
+++ b/hgext3rd/evolve/utility.py	Thu Dec 21 02:01:58 2017 +0100
@@ -36,3 +36,11 @@
         return (p2,)
     else:
         return parents
+
+def shouldwarmcache(repo):
+    configbool = repo.ui.configbool
+    if not configbool('experimental', 'obshashrange', False):
+        return False
+    if not configbool('experimental', 'obshashrange.warm-cache', True):
+        return False
+    return True