use std::{env, fs::File, io::Write, process::Command};

fn main() {
    let out_dir = env::var("OUT_DIR").unwrap();
    let mut f = File::create(format!("{}/built.rs", out_dir)).unwrap();

    let commit_hash = Command::new("git")
        .args(["rev-parse", "HEAD"])
        .output()
        .ok()
        .and_then(|o| String::from_utf8(o.stdout).ok())
        .unwrap_or_else(|| "unknown".into());

    writeln!(f, "#[allow(dead_code)]").unwrap();
    writeln!(
        f,
        "pub const GIT_COMMIT_HASH: &str = \"{}\";",
        commit_hash.trim()
    )
    .unwrap();
}