Merge branch 'jk/send-pack'

Merge branch 'jk/send-pack'

* jk/send-pack: (24 commits)
  send-pack: cluster ref status reporting
  send-pack: fix "everything up-to-date" message
  send-pack: tighten remote error reporting
  make "find_ref_by_name" a public function
  Fix warning about bitfield in struct ref
  send-pack: assign remote errors to each ref
  send-pack: check ref->status before updating tracking refs
  send-pack: track errors for each ref
  git-push: add documentation for the newly added --mirror mode
  Add tests for git push'es mirror mode
  Update the tracking references only if they were succesfully updated on remote
  Add a test checking if send-pack updated local tracking branches correctly
  git-push: plumb in --mirror mode
  Teach send-pack a mirror mode
  send-pack: segfault fix on forced push
  Reteach builtin-ls-remote to understand remotes
  send-pack: require --verbose to show update of tracking refs
  receive-pack: don't mention successful updates
  more terse push output
  Build in ls-remote
  ...