fn main() {
    let hash = std::process::Command::new("git")
        .args(["rev-parse", "--short", "HEAD"])
        .output()
        .ok()
        .and_then(|o| String::from_utf8(o.stdout).ok())
        .unwrap_or_default();
    let hash = hash.trim();
    println!("cargo:rustc-env=GIT_COMMIT={}", if hash.is_empty() { "unknown" } else { hash });
    println!("cargo:rerun-if-changed=.git/HEAD");
}