Merge branch 'jc/update-instead-into-void'

A push into an unborn branch, with "receive.denyCurrentBranch" set
to "updateInstead", did not check out the working tree as expected.

* jc/update-instead-into-void:
  push-to-deploy: allow pushing into an unborn branch and updating it

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

diff --cc t/t5516-fetch-push.sh
Simple merge