diff -r 6fb1d3c936d2 -r 6433da9c96a9 mercurial/cmdutil.py
--- a/mercurial/cmdutil.py	Tue Mar 15 09:51:42 2016 +0000
+++ b/mercurial/cmdutil.py	Wed Mar 23 10:50:24 2016 -0700
@@ -1597,10 +1597,12 @@
         raise error.Abort(inst.args[0])
     return t
 
-def showmarker(ui, marker):
+def showmarker(ui, marker, index=None):
     """utility function to display obsolescence marker in a readable way
 
     To be used by debug function."""
+    if index is not None:
+        ui.write("%i " % index)
     ui.write(hex(marker.precnode()))
     for repl in marker.succnodes():
         ui.write(' ')