Protocol switch from using generators to stream-like objects. This allows the the pull side to precisely control how much data is read so that another encapsulation layer is not needed. An http client gets a response with a finite size. Because ssh clients need to keep the stream open, we must not read more data than is sent in a response. But due to the streaming nature of the changegroup scheme, only the piece that's parsing the data knows how far it's allowed to read. This means the generator scheme isn't fine-grained enough. Instead we need file-like objects with a read(x) method. This switches everything for push/pull over to using file-like objects rather than generators.

pulling from ../a
searching for changes
warning: pulling from an unrelated repository!
adding changesets
adding manifests
adding file revisions
modified 1 files, added 1 changesets and 1 new revisions
(run 'hg update' to get a working copy)
changeset:   1:9a79c33a9db37480e40fbd2a65d62ebd2a3c441c
tag:         tip
user:        a
date:        Thu Jan  1 00:00:00 1970
summary:     a

changeset:   0:01f8062b2de51c0fa6428c5db1d1b3ea780189df
user:        b
date:        Thu Jan  1 00:00:00 1970
summary:     b