nushell/crates/nu-cli/src/git.rs

pub fn current_branch() -> Option<String> {
    #[cfg(feature = "git2")]
    {
        use git2::{Repository, RepositoryOpenFlags};
        use std::ffi::OsString;

        let v: Vec<OsString> = vec![];
        match Repository::open_ext(".", RepositoryOpenFlags::empty(), v) {
            Ok(repo) => {
                let r = repo.head();
                match r {
                    Ok(r) => match r.shorthand() {
                        Some(s) => Some(s.to_string()),
                        None => None,
                    },
                    _ => None,
                }
            }
            _ => None,
        }
    }
    #[cfg(not(feature = "git2"))]
    {
        None
    }
}