pub fn string_value(key: &str) -> Option<String>Expand description
Say once, per key, that a configured value could not be used.
Deduplicated because a key read twice in one run is a detail of how the
code is arranged, and repeating the warning would make it look like two
separate mistakes.
A free-form string key, policy-aware. Untyped reads have no --type
for git to refuse, so Bad cannot arise — this is Set-or-not.