use std::convert::TryInto; use git_hash::ObjectId; use crate::{    bstr::{BString, ByteSlice},    Head,}; impl<'repo> Head<'repo> {    /// Return a platform for obtaining iterators on the reference log associated with the `HEAD` reference.    pub fn log_iter(&self) -> git_ref::file::log::iter::Platform<'static, 'repo> {        git_ref::file::log::iter::Platform {            store: &self.repo.refs,            name: "HEAD".try_into().expect("HEAD is always valid"),            buf: Vec::new(),        }    }     /// Return a list of all branch names that were previously checked out with the first-ever checked out branch    /// being the first entry of the list, and the most recent is the last, along with the commit they were pointing to    /// at the time.    pub fn prior_checked_out_branches(&self) -> std::io::Result<Option<Vec<(BString, ObjectId)>>> {        Ok(self.log_iter().all()?.map(|log| {            log.filter_map(Result::ok)                .filter_map(|line| {                    line.message                        .strip_prefix(b"checkout: moving from ")                        .and_then(|from_to| from_to.find(" to ").map(|pos| &from_to[..pos]))                        .map(|from_branch| (from_branch.as_bstr().to_owned(), line.previous_oid()))                })                .collect()        }))    }}