Merge branch 'jt/fetch-large-handshake-window-on-http'

"git fetch" exchanges batched have/ack messages between the sender and the receiver, initially doubling every time and then falling back to enlarge the window size linearly. The "smart http" transport, being an half-duplex protocol, outgrows the preset limit too quickly and becomes inefficient when interacting with a large repository. The internal mechanism learned to grow the window size more aggressively when working with the "smart http" transport. * jt/fetch-large-handshake-window-on-http: fetch-pack: grow stateless RPC windows exponentially