pub fn precedence<T>(
cli: Option<T>,
file: Option<T>,
env: Option<T>,
) -> Option<T>Expand description
Resolves one setting across the three tiers, first Some wins.
The caller’s own built-in default is not a fourth argument here on
purpose: None from every tier means “nothing configured it,” and what
that becomes is specific to the setting (a fixed constant, a computed
value, or an outright refusal to start) in a way this function has no
business deciding.