Merge branch 'kn/fetch-push-bulk-ref-update' into jch

"git push" and "git fetch" are taught to update refs in batches to
gain performance.

Tentatively kicked out of 'next' to give its fix-up topic a chance to reboot.

* kn/fetch-push-bulk-ref-update:
  receive-pack: use batched reference updates
  send-pack: fix memory leak around duplicate refs
  fetch: use batched reference updates
  refs: add function to translate errors to strings

diff --cc builtin/fetch.c
Simple merge

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

diff --cc refs.c
Simple merge

diff --cc send-pack.c
Simple merge