Add missing local variable set.
Replace `>/dev/null 2>&1` by `&>/dev/null`.
Check return value of zstyle (if zero), instead of resulting string
value (if non-empty).
since we already have a function (`coalesce`) defined and both can now
get zcompiled into the same digest file.
Also, nest the `git-action` function to the scope where it's used.
that will be used by the minimal theme, and could be used for future
themes too. Prezto had this, but we diminished its necessity by
simplifying how git-info works.
