use bstr::{BStr, ByteSlice}; /// An unvalidated parse result of a key for a section, parsing input like `remote.origin` or `core`.#[derive(Debug, PartialEq, Ord, PartialOrd, Eq, Hash, Clone, Copy)]pub struct KeyRef<'a> {    /// The name of the section, like `remote` in `remote.origin`.    pub section_name: &'a str,    /// The name of the sub-section, like `origin` in `remote.origin`.    pub subsection_name: Option<&'a BStr>,} impl<'a> KeyRef<'a> {    /// Parse `input` like `remote.origin` or `core` as a `KeyRef` to make its section specific fields available,    /// or `None` if there were not one or two tokens separated by `.`.    /// Note that `input` isn't validated, and is `str` as ascii is a subset of UTF-8 which is required for any valid keys.    pub fn parse(input: &'a (impl crate::AsBStr + ?Sized)) -> Option<Self> {        let input = input.as_bstr();        let mut tokens = input.splitn(2, |b| *b == b'.');         Some(KeyRef {            section_name: tokens.next()?.to_str().ok()?,            subsection_name: tokens.next().map(Into::into),        })    }}