Merge branch 'bc/smart-http-atomic-push' into next

The atomic push over smart HTTP transport did not work, which has
been corrected.

* bc/smart-http-atomic-push:
  remote-curl: pass on atomic capability to remote side

diff --cc Documentation/gitremote-helpers.txt
Simple merge

diff --cc remote-curl.c
Simple merge

diff --cc t/t5541-http-push-smart.sh
Simple merge

diff --cc transport-helper.c
Simple merge