pub fn detect_format(path: Option<&Utf8Path>, content: &str) -> FormatExpand description
Detect the input format per ADR-0030 D4.
Precedence: file extension first (when path is Some), then
content fingerprint, then fallback to Format::Refs. The
caller’s explicit --format flag should short-circuit this
function — it is the slowest of the three precedence rules in the
ADR.