diff -r 6fb1d3c936d2 -r 6433da9c96a9 mercurial/commands.py
--- a/mercurial/commands.py	Tue Mar 15 09:51:42 2016 +0000
+++ b/mercurial/commands.py	Wed Mar 23 10:50:24 2016 -0700
@@ -3029,6 +3029,7 @@
          ('', 'record-parents', False,
           _('record parent information for the precursor')),
          ('r', 'rev', [], _('display markers relevant to REV')),
+         ('', 'index', False, _('display index of the marker')),
         ] + commitopts2,
          _('[OBSOLETED [REPLACEMENT ...]]'))
 def debugobsolete(ui, repo, precursor=None, *successors, **opts):
@@ -3091,8 +3092,9 @@
         else:
             markers = obsolete.getmarkers(repo)
 
-        for m in markers:
-            cmdutil.showmarker(ui, m)
+        for i, m in enumerate(markers):
+            ind = i if opts.get('index') else None
+            cmdutil.showmarker(ui, m, index=ind)
 
 @command('debugpathcomplete',
          [('f', 'full', None, _('complete an entire path')),