Merge branch 'jt/push-negotiation'

"git push" learns to discover common ancestor with the receiving
end over protocol v2.

* jt/push-negotiation:
  send-pack: support push negotiation
  fetch: teach independent negotiation (no packfile)
  fetch-pack: refactor command and capability write
  fetch-pack: refactor add_haves()
  fetch-pack: refactor process_acks()

diff --cc Documentation/technical/protocol-v2.txt
Simple merge

diff --cc builtin/fetch.c
Simple merge

diff --cc object.h
Simple merge

diff --cc t/t5701-git-serve.sh
index 73e74a9c5428a9deca67be72046fcde208b2e7c1,f03bb04803529971b8159b06ea98de057727f693..930721f053f1d1bb418fec18e547e51d3ae64719
--- 1/t/t5701-git-serve.sh
--- 2/t/t5701-git-serve.sh
+++ b/t/t5701-git-serve.sh
@@@ -16,10 -16,9 +16,10 @@@ test_expect_success 'test capability ad
        version 2
        agent=git/$(git version | cut -d" " -f3)
        ls-refs=unborn
-       fetch=shallow
+       fetch=shallow wait-for-done
        server-option
        object-format=$(test_oid algo)
 +      object-info
        0000
        EOF
  

diff --cc transport.c
Simple merge

diff --cc upload-pack.c
Simple merge