Merge branch 'aw/mirror-push' into jk/send-pack

Merge branch 'aw/mirror-push' into jk/send-pack

* aw/mirror-push:
  git-push: add documentation for the newly added --mirror mode
  Add tests for git push'es mirror mode
  git-push: plumb in --mirror mode
  Teach send-pack a mirror mode
  send-pack: segfault fix on forced push
  send-pack: require --verbose to show update of tracking refs
  receive-pack: don't mention successful updates
  more terse push output

Conflicts:

	transport.c
	transport.h