--- a/hgext3rd/evolve/obsdiscovery.py
+++ b/hgext3rd/evolve/obsdiscovery.py
@@ -393,16 +393,7 @@
     revs = scmutil.revrange(repo, opts['rev'])
     # prewarm depth cache
     repo.stablerange.warmup(repo, revs)
-    toproceed = [stablerange.stablerange(repo, r, 0, ) for r in revs]
-    ranges = set(toproceed)
-    while toproceed:
-        entry = toproceed.pop()
-        for r in entry.subranges():
-            if r not in ranges:
-                ranges.add(r)
-                toproceed.append(r)
-    ranges = list(ranges)
-    ranges.sort(key=lambda r: (-len(r), r.node))
+    ranges = stablerange.subrangesclosure(repo, revs)
     ui.status('rev         node index size depth      obshash\n')
     for r in ranges:
         d = (r.head, s(r.node), r.index, len(r), r.depth, node.short(r.obshash))

--- a/hgext3rd/evolve/stablerange.py
+++ b/hgext3rd/evolve/stablerange.py
@@ -132,6 +132,23 @@
 ### Stable Range computation  ###
 #################################
 
+def subrangesclosure(repo, heads):
+    """set of all standard subrange under heads
+
+    This is intended for debug purposes. Range are returned from largest to
+    smallest in terms of number of revision it contains."""
+    toproceed = [stablerange(repo, r, 0, ) for r in heads]
+    ranges = set(toproceed)
+    while toproceed:
+        entry = toproceed.pop()
+        for r in entry.subranges():
+            if r not in ranges:
+                ranges.add(r)
+                toproceed.append(r)
+    ranges = list(ranges)
+    ranges.sort(key=lambda r: (-len(r), r.node))
+    return ranges
+
 class stablerangecache(dict):
 
     def __init__(self):