use git_odb::alternate;use std::{    fs, io,    path::{Path, PathBuf},}; fn alternate(objects_at: impl Into<PathBuf>, objects_to: impl Into<PathBuf>) -> Result<(PathBuf, PathBuf), io::Error> {    alternate_with(objects_at, objects_to, None)} fn alternate_with(    objects_at: impl Into<PathBuf>,    objects_to: impl Into<PathBuf>,    content_before_to: Option<&str>,) -> Result<(PathBuf, PathBuf), io::Error> {    let at = objects_at.into();    let to = objects_to.into();    let at_info = at.join("info");    fs::create_dir_all(&at_info)?;    fs::create_dir_all(&to)?;    let contents = if let Some(content) = content_before_to {        let mut c = vec![b'\n'];        c.extend(content.as_bytes());        c.extend(to.to_string_lossy().as_bytes());        c    } else {        to.to_string_lossy().as_bytes().to_owned()    };    fs::write(at_info.join("alternates"), contents)?;    Ok((at, to))} #[test]fn circular_alternates_are_detected_with_relative_paths() -> crate::Result {    let tmp = tempdir::TempDir::new("alternates")?;    let (from, _) = alternate(tmp.path().join("a"), tmp.path().join("b"))?;    alternate(tmp.path().join("b"), Path::new("..").join("a"))?;     match alternate::resolve(&from) {        Err(alternate::Error::Cycle(chain)) => {            assert_eq!(                chain                    .into_iter()                    .map(|p| p.file_name().expect("non-root").to_str().expect("utf8").to_owned())                    .collect::<Vec<_>>(),                vec!["a", "b"]            );        }        _ => unreachable!("should be a specific kind of error"),    }    Ok(())} #[test]fn single_link_with_comment_before_path_and_ansi_c_escape() -> crate::Result {    let tmp = tempdir::TempDir::new("alternates")?;    let non_alternate = tmp.path().join("actual");     // let (from, to) = alternate_with(tmp.path().join("a"), non_alternate, Some("# comment\n\"../a\"\n"))?;    let (from, to) = alternate_with(tmp.path().join("a"), non_alternate, Some("# comment\n"))?;    let alternates = alternate::resolve(from)?;    assert_eq!(alternates.len(), 1);    assert_eq!(alternates[0].loose.path, to);    Ok(())} #[test]fn no_alternate_in_first_objects_dir() -> crate::Result {    let tmp = tempdir::TempDir::new("alternates")?;    assert!(alternate::resolve(tmp.path())?.is_empty());    Ok(())}