use std::path::{Path, PathBuf}; #[derive(Debug, thiserror::Error)]pub enum Error {    #[error("Could not find a valid HEAD reference")]    FindHeadRef(#[from] git_ref::file::find::existing::Error),    #[error("Expected HEAD at '.git/HEAD', got '.git/{}'", .name)]    MisplacedHead { name: bstr::BString },    #[error("Expected an objects directory at '{}'", .missing.display())]    MissingObjectsDirectory { missing: PathBuf },    #[error("Expected a refs directory at '{}'", .missing.display())]    MissingRefsDirectory { missing: PathBuf },} /// Returns true if the given `git_dir` seems to be a bare repository.////// Please note that repositories without any file in their work tree will also appear bare.pub fn is_bare(git_dir: impl AsRef<Path>) -> bool {    !git_dir.as_ref().join("index").exists()} /// What constitutes a valid git repository, and what's yet to be implemented, returning the guessed repository kind/// purely based on the presence of files. Note that the git-config ultimately decides what's bare.////// * [x] a valid head/// * [ ] git common directory///   * [ ] respect GIT_COMMON_DIR/// * [x] an objects directory///   * [x] respect GIT_OBJECT_DIRECTORY/// * [x] a refs directorypub fn is_git(git_dir: impl AsRef<Path>) -> Result<crate::Kind, Error> {    let dot_git = git_dir.as_ref();     {        let refs = git_ref::file::Store::at(&dot_git, Default::default());        let head = refs.find_loose("HEAD")?;        if head.name.as_bstr() != "HEAD" {            return Err(Error::MisplacedHead {                name: head.name.into_inner(),            });        }    }     {        let objects_path = std::env::var("GIT_OBJECT_DIRECTORY")            .map(PathBuf::from)            .unwrap_or_else(|_| dot_git.join("objects"));        if !objects_path.is_dir() {            return Err(Error::MissingObjectsDirectory { missing: objects_path });        }    }    {        let refs_path = dot_git.join("refs");        if !refs_path.is_dir() {            return Err(Error::MissingRefsDirectory { missing: refs_path });        }    }     Ok(if is_bare(git_dir) {        crate::Kind::Bare    } else {        crate::Kind::WorkTree    })}