//! Record build metadata (git commit and branch) at compile time so the
//! 'am version' command can display it, like Nushell's version table.
//!
//! When git is unavailable (e.g. building from a source tarball) the values
//! are simply empty.

use std::process::Command;

fn git(args: &[&str]) -> String {
    Command::new("git")
        .args(args)
        .output()
        .ok()
        .filter(|o| o.status.success())
        .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_string())
        .unwrap_or_default()
}

fn main() {
    println!("cargo:rerun-if-changed=.git/HEAD");
    println!("cargo:rerun-if-changed=.git/refs/heads");
    let commit = git(&["rev-parse", "HEAD"]);
    let branch = git(&["rev-parse", "--abbrev-ref", "HEAD"]);
    // A detached HEAD reports the literal branch name "HEAD".
    let branch = if branch == "HEAD" {
        String::new()
    } else {
        branch
    };
    println!("cargo:rustc-env=AM_GIT_COMMIT={commit}");
    println!("cargo:rustc-env=AM_GIT_BRANCH={branch}");
}