--- a/hgext3rd/evolve/__init__.py	Wed May 10 13:04:31 2017 +0200
+++ b/hgext3rd/evolve/__init__.py	Wed May 10 11:52:11 2017 +0200
@@ -3261,15 +3261,18 @@
 
 @eh.command(
     '^debugobshistory',
-    [('r', 'rev', [], _("revision to debug"))],
-    _('hg debugobshistory [OPTION]... [-r] [REV]'))
+    [] + commands.formatteropts,
+    _('hg debugobshistory [OPTION]... [REV]'))
 def debugobshistory(ui, repo, *revs, **opts):
     revs = scmutil.revrange(repo, revs)
+    fm = ui.formatter('debugobshistory', opts)
 
     for rev in revs:
-        _debugobshistorysingle(ui, repo, rev)
-
-def _debugobshistorysingle(ui, repo, rev):
+        _debugobshistorysingle(ui, fm, repo, rev)
+
+    fm.end()
+
+def _debugobshistorysingle(ui, fm, repo, rev):
     """ Display the obsolescence history for a single revision
     """
     precursors = repo.obsstore.precursors
@@ -3279,41 +3282,66 @@
 
     while nodes:
         ctxnode = nodes.pop()
-        _debugobshistorydisplaynode(ui, repo, ctxnode)
+        _debugobshistorydisplaynode(ui, fm, repo, ctxnode)
 
         succs = successors.get(ctxnode, ())
 
+        markerfm = fm.nested("debugobshistory.markers")
         for successor in sorted(succs):
-            _debugobshistorydisplaymarker(ui, repo, successor)
+            _debugobshistorydisplaymarker(ui, markerfm, repo, successor)
+        markerfm.end()
 
         precs = precursors.get(ctxnode, ())
         nodes.extend(precursor[0] for precursor in sorted(precs))
 
-def _debugobshistorydisplaynode(ui, repo, node):
+def _debugobshistorydisplaynode(ui, fm, repo, node):
     ctx = repo.unfiltered()[node]
     shortdescription = ctx.description().splitlines()[0]
 
-    args = (ui.label(str(ctx), "evolve.short_node"),
-            ui.label(str(int(ctx)), "evolve.rev"),
-            ui.label(shortdescription, "evolve.short_description"))
-
-    ui.write("%s (%s) %s\n" % args)
-
-def _debugobshistorydisplaymarker(ui, repo, marker):
+    fm.startitem()
+    fm.write('debugobshistory.node', '%s', str(ctx),
+             label="evolve.short_node")
+    fm.plain(' ')
+
+    fm.write('debugobshistory.rev', '(%d)', int(ctx),
+             label="evolve.rev")
+    fm.plain(' ')
+
+    fm.write('debugobshistory.shortdescription', '%s', shortdescription,
+             label="evolve.short_description")
+    fm.plain('\n')
+
+def _debugobshistorydisplaymarker(ui, fm, repo, marker):
     succnodes = marker[1]
     date = marker[4]
     metadata = dict(marker[3])
 
-    msgargs = (ui.label(metadata['user'], "evolve.user"),
-               ui.label(util.datestr(date), "evolve.date"))
-    # If no successors with a marker, the commit has been pruned
+    fm.startitem()
+    fm.plain('  ')
+
+    # Detect pruned revisions
     if len(succnodes) == 0:
-        msgargs = (ui.label("pruned", "evolve.verb"),) + msgargs
-        msg = "  %s by %s (%s)\n"
+        verb = 'pruned'
     else:
+        verb = 'rewritten'
+
+    fm.write('debugobshistory.verb', '%s', verb,
+             label="evolve.verb")
+    fm.plain(' by ')
+
+    fm.write('debugobshistory.marker_user', '%s', metadata['user'],
+             label="evolve.user")
+    fm.plain(' ')
+
+    fm.write('debugobshistory.marker_date', '(%s)', fm.formatdate(date),
+             label="evolve.date")
+
+    if len(succnodes) > 0:
+        fm.plain(' as ')
+
         shortsnodes = (node.short(succnode) for succnode in sorted(succnodes))
-        labelednodes = (ui.label(node, "evolve.short_node") for node in shortsnodes)
-        msgargs = (ui.label("rewritten", "evolve.verb"),) + msgargs + (", ".join(labelednodes),)
-        msg = "  %s by %s (%s) as %s\n"
-
-    ui.write(msg % msgargs)
+        nodes = fm.formatlist(shortsnodes, 'debugobshistory.succnodes', sep=', ')
+        fm.write('debugobshistory.succnodes', '%s', nodes,
+                 label="evolve.short_node")
+
+    fm.plain("\n")