--- a/hgext/evolve.py	Tue Sep 02 20:11:45 2014 +0200
+++ b/hgext/evolve.py	Wed Sep 03 23:56:39 2014 +0200
@@ -2254,19 +2254,38 @@
         topic = 'OBSEXC'
     ui.progress(topic, *args, **kwargs)
 
-@eh.wrapfunction(exchange, '_pushdiscoveryobsmarkers')
-def _pushdiscoveryobsmarkers(orig, pushop):
-    if (obsolete._enabled
-        and pushop.repo.obsstore
-        and 'obsolete' in pushop.remote.listkeys('namespaces')):
-        repo = pushop.repo
-        obsexcmsg(repo.ui, "computing relevant nodes\n")
-        revs = list(repo.revs('::%ln', pushop.futureheads))
-        unfi = repo.unfiltered()
-        cl = unfi.changelog
-        if not pushop.remote.capable('_evoext_obshash_0'):
-            # do not trust core yet
-            # return orig(pushop)
+if getattr(exchange, '_pushdiscoveryobsmarkers', None) is not None:
+    @eh.wrapfunction(exchange, '_pushdiscoveryobsmarkers')
+    def _pushdiscoveryobsmarkers(orig, pushop):
+        if (obsolete._enabled
+            and pushop.repo.obsstore
+            and 'obsolete' in pushop.remote.listkeys('namespaces')):
+            repo = pushop.repo
+            obsexcmsg(repo.ui, "computing relevant nodes\n")
+            revs = list(repo.revs('::%ln', pushop.futureheads))
+            unfi = repo.unfiltered()
+            cl = unfi.changelog
+            if not pushop.remote.capable('_evoext_obshash_0'):
+                # do not trust core yet
+                # return orig(pushop)
+                nodes = [cl.node(r) for r in revs]
+                if nodes:
+                    obsexcmsg(repo.ui, "computing markers relevant to %i nodes\n"
+                                       % len(nodes))
+                    pushop.outobsmarkers = repo.obsstore.relevantmarkers(nodes)
+                else:
+                    obsexcmsg(repo.ui, "markers already in sync\n")
+                    pushop.outobsmarkers = []
+                    pushop.outobsmarkers = repo.obsstore.relevantmarkers(nodes)
+                return
+
+            common = []
+            obsexcmsg(repo.ui, "looking for common markers in %i nodes\n"
+                               % len(revs))
+            commonrevs = list(unfi.revs('::%ln', pushop.outgoing.commonheads))
+            common = findcommonobsmarkers(pushop.ui, unfi, pushop.remote, commonrevs)
+
+            revs = list(unfi.revs('%ld - (::%ln)', revs, common))
             nodes = [cl.node(r) for r in revs]
             if nodes:
                 obsexcmsg(repo.ui, "computing markers relevant to %i nodes\n"
@@ -2275,24 +2294,6 @@
             else:
                 obsexcmsg(repo.ui, "markers already in sync\n")
                 pushop.outobsmarkers = []
-                pushop.outobsmarkers = repo.obsstore.relevantmarkers(nodes)
-            return
-
-        common = []
-        obsexcmsg(repo.ui, "looking for common markers in %i nodes\n"
-                           % len(revs))
-        commonrevs = list(unfi.revs('::%ln', pushop.outgoing.commonheads))
-        common = findcommonobsmarkers(pushop.ui, unfi, pushop.remote, commonrevs)
-
-        revs = list(unfi.revs('%ld - (::%ln)', revs, common))
-        nodes = [cl.node(r) for r in revs]
-        if nodes:
-            obsexcmsg(repo.ui, "computing markers relevant to %i nodes\n"
-                               % len(nodes))
-            pushop.outobsmarkers = repo.obsstore.relevantmarkers(nodes)
-        else:
-            obsexcmsg(repo.ui, "markers already in sync\n")
-            pushop.outobsmarkers = []
 
 @eh.wrapfunction(wireproto, 'capabilities')
 def discocapabilities(orig, repo, proto):
@@ -2311,10 +2312,14 @@
         return discocapabilities(oldcap, repo, proto)
     wireproto.commands['capabilities'] = (newcap, args)
     wireproto.commands['evoext_obshash'] = (srv_obshash, 'nodes')
-    olddisco = exchange.pushdiscoverymapping['obsmarker']
-    def newdisco(pushop):
-        _pushdiscoveryobsmarkers(olddisco, pushop)
-    exchange.pushdiscoverymapping['obsmarker'] = newdisco
+    if getattr(exchange, '_pushdiscoveryobsmarkers', None) is None:
+        ui.warn('evolve: your mercurial version is too old\n'
+                'evolve: (running in degraded mode, push will includes all markers)\n')
+    else:
+        olddisco = exchange.pushdiscoverymapping['obsmarker']
+        def newdisco(pushop):
+            _pushdiscoveryobsmarkers(olddisco, pushop)
+        exchange.pushdiscoverymapping['obsmarker'] = newdisco
 
 ### Set discovery START
 
@@ -2558,20 +2563,21 @@
             kwargs['evo_obscommon'] = common
     return ret
 
-@eh.wrapfunction(exchange, '_getbundleobsmarkerpart')
-def _getbundleobsmarkerpart(orig, bundler, repo, source, heads=None, common=None,
-                            bundlecaps=None, **kwargs):
-    if 'evo_obscommon' not in kwargs:
-        return orig(bundler, repo, source, heads, common, bundlecaps, **kwargs)
+if getattr(exchange, '_getbundleobsmarkerpart', None) is not None:
+    @eh.wrapfunction(exchange, '_getbundleobsmarkerpart')
+    def _getbundleobsmarkerpart(orig, bundler, repo, source, heads=None, common=None,
+                                bundlecaps=None, **kwargs):
+        if 'evo_obscommon' not in kwargs:
+            return orig(bundler, repo, source, heads, common, bundlecaps, **kwargs)
 
-    if kwargs.get('obsmarkers', False):
-        if heads is None:
-            heads = repo.heads()
-        obscommon = kwargs.get('evo_obscommon', ())
-        obsset = repo.set('::%ln - ::%ln', heads, obscommon)
-        subset = [c.node() for c in obsset]
-        markers = repo.obsstore.relevantmarkers(subset)
-        exchange.buildobsmarkerspart(bundler, markers)
+        if kwargs.get('obsmarkers', False):
+            if heads is None:
+                heads = repo.heads()
+            obscommon = kwargs.get('evo_obscommon', ())
+            obsset = repo.set('::%ln - ::%ln', heads, obscommon)
+            subset = [c.node() for c in obsset]
+            markers = repo.obsstore.relevantmarkers(subset)
+            exchange.buildobsmarkerspart(bundler, markers)
 
 
 @eh.wrapfunction(exchange, '_pullobsolete')