bundle2-push: extract changegroup logic in its own function

We extract the creation of changegroup related parts into its own function.
This precludes the inclusion of more diverse data during the bundle2 push.

We use a closure to carry the logic that need to be perform when processing the
server reply.

mercurial/exchange.py

@@ -203,6 +203,23 b' def _pushcheckoutgoing(pushop):'
                              newbm)
     return True
 
+def _pushb2ctx(pushop, bundler):
+    """handle changegroup push through bundle2
+
+    addchangegroup result is stored in the ``pushop.ret`` attribute.
+    """
+    # Send known heads to the server for race detection.
+    if not pushop.force:
+        bundler.newpart('B2X:CHECK:HEADS', data=iter(pushop.remoteheads))
+    cg = changegroup.getlocalbundle(pushop.repo, 'push', pushop.outgoing)
+    cgpart = bundler.newpart('B2X:CHANGEGROUP', data=cg.getchunks())
+    def handlereply(op):
+        """extract addchangroup returns from server reply"""
+        cgreplies = op.records.getreplies(cgpart.id)
+        assert len(cgreplies['changegroup']) == 1
+        pushop.ret = cgreplies['changegroup'][0]['return']
+    return handlereply
+
 def _pushbundle2(pushop):
     """push data to the remote using bundle2
 
@@ -213,12 +230,8 b' def _pushbundle2(pushop):'
     capsblob = bundle2.encodecaps(pushop.repo.bundle2caps)
     bundler.newpart('b2x:replycaps', data=capsblob)
     extrainfo = _pushbundle2extraparts(pushop, bundler)
-    # Send known heads to the server for race detection.
-    if not pushop.force:
-        bundler.newpart('B2X:CHECK:HEADS', data=iter(pushop.remoteheads))
     # add the changegroup bundle
-    cg = changegroup.getlocalbundle(pushop.repo, 'push', pushop.outgoing)
-    cgpart = bundler.newpart('B2X:CHANGEGROUP', data=cg.getchunks())
+    cgreplyhandler = _pushb2ctx(pushop, bundler)
     stream = util.chunkbuffer(bundler.getchunks())
     try:
         reply = pushop.remote.unbundle(stream, ['force'], 'push')
@@ -228,9 +241,7 b' def _pushbundle2(pushop):'
         op = bundle2.processbundle(pushop.repo, reply)
     except error.BundleValueError, exc:
         raise util.Abort('missing support for %s' % exc)
-    cgreplies = op.records.getreplies(cgpart.id)
-    assert len(cgreplies['changegroup']) == 1
-    pushop.ret = cgreplies['changegroup'][0]['return']
+    cgreplyhandler(op)
     _pushbundle2extrareply(pushop, op, extrainfo)
 
 def _pushbundle2extraparts(pushop, bundler):