pub struct Engine {    repo: gix::Repository,    con: rusqlite::Connection,    commits: Vec<gix::ObjectId>,} pub struct Options {    pub object_cache_size_mb: usize,    pub find_copies_harder: bool,    pub threads: Option<usize>,} mod db; mod engine;pub use engine::Command; pub fn prepare(    repo_dir: &std::path::Path,    mut progress: impl gix::Progress,    err: impl std::io::Write,    opts: Options,) -> anyhow::Result<Engine> {    let repo = gix::discover(repo_dir)?;    let mut con = db::create(repo.git_dir().join("ein.query"))?;    let commits = engine::update(&repo, &mut con, &mut progress, err, opts)?;    Ok(Engine { repo, con, commits })}