use anyhow::Context;use gix::{ObjectId, objs::Kind}; pub fn function(mut repo: gix::Repository, spec: Option<String>, mut out: impl std::io::Write) -> anyhow::Result<()> {    let spec = spec.unwrap_or("HEAD".into());     repo.object_cache_size_if_unset(4 * 1024 * 1024);    // We expect to be finding a bunch of non-existent objects here - never refresh the ODB    repo.objects.refresh_never();     let id = repo        .rev_parse_single(spec.as_str())        .context("Only single revisions are supported")?;    let commits: gix::revision::Walk<'_> = id        .object()?        .peel_to_kind(gix::object::Kind::Commit)        .context("Need committish as starting point")?        .id()        .ancestors()        .all()?;     let on_missing = |oid: &ObjectId, kind: Kind| {        writeln!(out, "{oid}: {kind}").expect("failed to write output");    };     let mut check = gix_fsck::Connectivity::new(&repo.objects, on_missing);    // Walk all commits, checking each one for connectivity    for commit in commits {        let commit = commit?;        check.check_commit(&commit.id)?;        // Note that we leave parent-iteration to the commits iterator, as it will        // correctly handle shallow repositories which are expected to have the commits        // along the shallow boundary missing.    }    Ok(())}