clone a Repo, The memory has increased from 1m to 20m and will not be released

I use this code to clone repo, The memory has increased from 1m to >20m and more。And will not be released

fn clone(){

    let mut callbacks = RemoteCallbacks::new();

    callbacks.credentials(|_url, username_from_url, _allowed_types| {
        Cred::userpass_plaintext("abc","abcd)
    });

    // Prepare fetch options.
    let mut fo = git2::FetchOptions::new();
    fo.remote_callbacks(callbacks);

    // Prepare builder.
    let mut builder = git2::build::RepoBuilder::new();
    builder.fetch_options(fo);

    let r= builder.clone(
        "http://xxxx.git",
        Path::new("/code-analyse/"),
    );

    match r{
        Ok(repo) => {println!("ok") }
        Err(e) => {println!("{}",e)}
    }
}

Start by reproducing the reported growth in the shown clone function using git2::build::RepoBuilder::clone and monitor memory before and after the operation. Trace the clone and fetch path used by RepoBuilder, then verify that repeated clones release memory and add or run a focused regression test if the repository provides one.