zsh completion for `git push origin --delete`

The man for `--delete` says only refs on the remote repo are affected.
Then, the auto-completion in zsh shall not return local refs.

$ git branch -a
  master
* tmp
  remotes/origin/master
  remotes/origin/tmp

$ git push origin --delete <tab>
FETCH_HEAD     HEAD           master         ORIG_HEAD
origin/master  origin/tmp     tmp

I feel hitting <tab> shall only return `master` and `tmp`, which are
the valid input `--delete` option.

git version 2.2.2

-- 
Best Regards

Yours faithfully
Albert Netymk