Merge branch 'bw/clone-ref-prefixes'

The wire-protocol v2 relies on the client to send "ref prefixes" to
limit the bandwidth spent on the initial ref advertisement.  "git
clone" when learned to speak v2 forgot to do so, which has been
corrected.

* bw/clone-ref-prefixes:
clone: send ref-prefixes when using protocol v2

diff --cc builtin/clone.c
Simple merge