--- a/mercurial/wireproto.py	Thu Apr 16 22:33:53 2015 +0900
+++ b/mercurial/wireproto.py	Thu Apr 16 20:57:51 2015 -0500
@@ -363,8 +363,10 @@
             opts[key] = value
         f = self._callcompressable("getbundle", **opts)
         bundlecaps = kwargs.get('bundlecaps')
-        if bundlecaps is not None and 'HG2Y' in bundlecaps:
-            return bundle2.unbundle20(self.ui, f)
+        if bundlecaps is None:
+            bundlecaps = () # kwargs could have it to None
+        if util.any((cap.startswith('HG2') for cap in bundlecaps)):
+            return bundle2.getunbundler(self.ui, f)
         else:
             return changegroupmod.cg1unpacker(f, 'UN')
 
@@ -401,7 +403,7 @@
         else:
             # bundle2 push. Send a stream, fetch a stream.
             stream = self._calltwowaystream('unbundle', cg, heads=heads)
-            ret = bundle2.unbundle20(self.ui, stream)
+            ret = bundle2.getunbundler(self.ui, stream)
         return ret
 
     def debugwireargs(self, one, two, three=None, four=None, five=None):
@@ -613,9 +615,9 @@
         # otherwise, add 'streamreqs' detailing our local revlog format
         else:
             caps.append('streamreqs=%s' % ','.join(requiredformats))
-    if repo.ui.configbool('experimental', 'bundle2-exp', False):
+    if repo.ui.configbool('experimental', 'bundle2-advertise', True):
         capsblob = bundle2.encodecaps(bundle2.getrepocaps(repo))
-        caps.append('bundle2-exp=' + urllib.quote(capsblob))
+        caps.append('bundle2=' + urllib.quote(capsblob))
     caps.append('unbundle=%s' % ','.join(changegroupmod.bundlepriority))
     caps.append('httpheader=1024')
     return caps
@@ -839,35 +841,40 @@
         finally:
             fp.close()
             os.unlink(tempname)
-    except error.BundleValueError, exc:
-            bundler = bundle2.bundle20(repo.ui)
-            errpart = bundler.newpart('b2x:error:unsupportedcontent')
+
+    except (error.BundleValueError, util.Abort, error.PushRaced), exc:
+        # handle non-bundle2 case first
+        if not getattr(exc, 'duringunbundle2', False):
+            try:
+                raise
+            except util.Abort:
+                # The old code we moved used sys.stderr directly.
+                # We did not change it to minimise code change.
+                # This need to be moved to something proper.
+                # Feel free to do it.
+                sys.stderr.write("abort: %s\n" % exc)
+                return pushres(0)
+            except error.PushRaced:
+                return pusherr(str(exc))
+
+        bundler = bundle2.bundle20(repo.ui)
+        for out in getattr(exc, '_bundle2salvagedoutput', ()):
+            bundler.addpart(out)
+        try:
+            raise
+        except error.BundleValueError, exc:
+            errpart = bundler.newpart('error:unsupportedcontent')
             if exc.parttype is not None:
                 errpart.addparam('parttype', exc.parttype)
             if exc.params:
                 errpart.addparam('params', '\0'.join(exc.params))
-            return streamres(bundler.getchunks())
-    except util.Abort, inst:
-        # The old code we moved used sys.stderr directly.
-        # We did not change it to minimise code change.
-        # This need to be moved to something proper.
-        # Feel free to do it.
-        if getattr(inst, 'duringunbundle2', False):
-            bundler = bundle2.bundle20(repo.ui)
-            manargs = [('message', str(inst))]
+        except util.Abort, exc:
+            manargs = [('message', str(exc))]
             advargs = []
-            if inst.hint is not None:
-                advargs.append(('hint', inst.hint))
-            bundler.addpart(bundle2.bundlepart('b2x:error:abort',
+            if exc.hint is not None:
+                advargs.append(('hint', exc.hint))
+            bundler.addpart(bundle2.bundlepart('error:abort',
                                                manargs, advargs))
-            return streamres(bundler.getchunks())
-        else:
-            sys.stderr.write("abort: %s\n" % inst)
-            return pushres(0)
-    except error.PushRaced, exc:
-        if getattr(exc, 'duringunbundle2', False):
-            bundler = bundle2.bundle20(repo.ui)
-            bundler.newpart('b2x:error:pushraced', [('message', str(exc))])
-            return streamres(bundler.getchunks())
-        else:
-            return pusherr(str(exc))
+        except error.PushRaced, exc:
+            bundler.newpart('error:pushraced', [('message', str(exc))])
+        return streamres(bundler.getchunks())