The goal with these changes was to give users a clearer, more readable
interface, so we should present that interface up front and only
document the aliases as a backward-compatibility option.
I've renamed the envconfig tags to reflect the switch, but I left the
actual field names the same. I think they're sufficiently meaningful
inside the code, and leaving them unchanged avoids making a bunch of
churn in the rest of the code.
a5342d7bac