zsh completion for “git log”

Question

When I type:

git log p<tab>

In Bash it expands it to git log production/master (if there's only one branch at existing production remote).

How can I have zsh behave like that?

EDIT:

This does not work either:

git sub<tab>

(it should complete to git submodule).

Answer 1

It seems zsh version 4.3.10 had some troubles with that. Upgrading to 4.3.12 solved it!