use git_repository as git; use crate::commit::Message; /// A head reference will all commits that are 'governed' by it, that is are in its exclusive ancestry.pub struct Segment<'a> {    pub head: git::refs::Reference,    /// only relevant history items, that is those that change code in the respective crate.    pub history: Vec<&'a Item>,} pub struct Item {    pub id: git::ObjectId,    pub message: Message,    pub commit_time: git::actor::Time,    pub tree_id: git::ObjectId,    pub parent_tree_id: Option<git::ObjectId>,} #[cfg(test)]mod tests {    use super::*;     #[test]    fn size_of_item() {        assert_eq!(            std::mem::size_of::<Item>(),            200,            "there are plenty of these loaded at a time and we should not let it grow unnoticed."        )    }}