getbundle: add a ``cg`` boolean argument to control changegroup inclusion The ``getbundle`` function was initially design to return a changegroup bundle. However, bundle2 allows transmitting a wide range of data. Some bundle2 requests may not include a changegroup at all. Before this changeset, the client would request a changegroup for ``heads=[nullid]`` and receive an empty changegroup. We introduce an official boolean parameter, ``cg``, that can be set to false to disable changegroup generation on getbundle. A new bundle2 capability is introduced to let the client know.

--- a/mercurial/localrepo.py	Thu May 22 17:20:52 2014 -0700
+++ b/mercurial/localrepo.py	Sat May 31 16:48:29 2014 -0700
@@ -182,7 +182,9 @@
 
     bundle2caps = {'HG2X': (),
                    'b2x:listkeys': (),
-                   'b2x:pushkey': ()}
+                   'b2x:pushkey': (),
+                   'b2x:changegroup': (),
+                  }
 
     # a list of (ui, featureset) functions.
     # only functions defined in module of enabled extensions are invoked