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

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