wireproto: document the wonky push protocol for SSH It took me several minutes to figure out how the "unbundle" protocol worked. It turns out that the SSH protocol handler sends an empty reply that is interpreted as "OK to send" and only then does the client send the bundle payload. On top of that, the response is different depending on whether the operation was successful or not. I nearly pulled out my hair deciphering this. Differential Revision: https://phab.mercurial-scm.org/D2385