//! Build script: records the git commit cumulus is built from, so
//! `cumulus --version` can tell exactly which build you're running.
//!
//! Outside a git checkout, or without git installed, the commit is "unknown".
//! (No Windows icon or manifest: a terminal program's icon only shows in
//! Explorer, and a manifest changes nothing for it.)

use std::path::Path;
use std::process::Command;

fn main() {
    let commit = git_commit().unwrap_or_else(|| "unknown".to_string());
    println!("cargo::rustc-env=CUMULUS_COMMIT={commit}");

    // Run again when the commit changes: HEAD moves on checkout, and the
    // branch files change on commit. Only watch files that exist, or cargo
    // would run this script on every build.
    println!("cargo::rerun-if-changed=build.rs");
    for path in [".git/HEAD", ".git/refs/heads", ".git/packed-refs"] {
        if Path::new(path).exists() {
            println!("cargo::rerun-if-changed={path}");
        }
    }
}

/// The short hash of the current commit, if git can tell.
fn git_commit() -> Option<String> {
    let output = Command::new("git").args(["rev-parse", "--short=9", "HEAD"]).output().ok()?;
    let hash = String::from_utf8(output.stdout).ok()?;
    let hash = hash.trim();
    (output.status.success() && !hash.is_empty()).then(|| hash.to_string())
}