fn main() {     // https://doc.rust-lang.org/stable/cargo/reference/build-scripts.html
    //println!("cargo:rerun-if-changed=build.rs");    // XXX: prevent re-run indead
    // By default, cargo always re-run the build script if any file within the package
    // is changed, and no any rerun-if instruction is emitted.
    println!("cargo:rerun-if-changed=src");
    println!("cargo:rustc-env=BUILD_TIMESTAMP={}",
        chrono::Local::now().format("%H:%M:%S%z %Y-%m-%d"));

    let output = std::process::Command::new("git")
        .args(["rev-parse", "--short", "HEAD"]).output().unwrap();
    println!("cargo:rustc-env=BUILD_GIT_HASH={}", String::from_utf8(output.stdout).unwrap());
    println!("cargo:rerun-if-changed={}", std::path::Path::new(".git").join("index").display());
}