Merge branch 'mm/push-default-warning'

Across the transition at around Git version 2.0, the user used to
get a pretty loud warning when running "git push" without setting
push.default configuration variable.  We no longer warn, given that
the transition is over long time ago.

* mm/push-default-warning:
  push: remove "push.default is unset" warning message

diff --cc builtin/push.c
Simple merge