Merge branch 'jk/fix-proto-downgrade-to-v0'

Transports that do not support protocol v2 did not correctly fall
back to protocol v0 under certain conditions, which has been
corrected.

* jk/fix-proto-downgrade-to-v0:
  git_connect(): fix corner cases in downgrading v2 to v0

diff --cc builtin/fetch-pack.c
Simple merge

diff --cc builtin/send-pack.c
Simple merge

diff --cc connect.c
Simple merge

diff --cc connect.h
Simple merge

diff --cc remote-curl.c
Simple merge

diff --cc t/t5702-protocol-v2.sh
Simple merge

diff --cc transport.c
Simple merge