Auto merge of #7060 - lzutao:zsh-complete-package, r=ehuss

_cargo: Make function style consistent

They are just white-space changes. I'm planning to bring back Zsh completion
for `-p` (package) option, which was disabled in #1713. This PR is the first
stepping stone towards that goal.

A disadvantageous is that I am just starting to learn Zsh completion system.
Guess how far can I go?

r? @ehuss