pushkey: add a ``decode`` function This function is just a shorthand for ``decoding.fromlocal``. It will help hiding the encoding business from other code exchanging pushkey data over the wire.

pull: when remote supports it, pull phase data alongside changesets We use bundle2 to retrieve the remote phase data at the same time as changesets. This reduces the amount of requestis and should improve consistency as the server can ensure nothing changed between the retrieval of those parts.

getbundle: support of listkeys argument when bundle2 is used A new ``listkeys`` is supported by getbundle. It is a list of namespaces whose content should be included in the bundle. An appropriate entry has been added to the wireproto map of getbundle arguments and a new bundle2 capability is advertised. There are still no codes that request such parts in core mercurial.

getbundle: raise error if extra arguments are provided for bundle10 New arguments are most likely to be supported by bundle20 (and above) only.

bundle: introduce a listkey handler This makes it possible to handle listkeys-related data stored in a bundle2. There are no producers yet.

pull: split remote phases retrieval from actual application We want to be able to retrieve phases information through bundle2. The logic to apply remote phases will not change.

wireproto: use pushkey.decodekey