//! Build script for `nbd`.
//!
//! Captures the short git SHA at compile time and emits it as the
//! `GIT_SHORT_SHA` environment variable, making it available via
//! `env!("GIT_SHORT_SHA")` in the crate source.
//!
//! Falls back to `"unknown"` when git is unavailable (e.g. a clean Nix
//! sandbox build where `.git/` is not present).

fn main() {
    // Capture the short git SHA at build time.
    let sha = std::process::Command::new("git")
        .args(["rev-parse", "--short", "HEAD"])
        .output()
        .ok()
        .and_then(|o| {
            if o.status.success() {
                Some(o.stdout)
            } else {
                None
            }
        })
        .and_then(|b| String::from_utf8(b).ok())
        .map(|s| s.trim().to_string())
        .unwrap_or_else(|| "unknown".to_string());

    println!("cargo:rustc-env=GIT_SHORT_SHA={sha}");
    // Re-run whenever HEAD or any ref changes (new commits, branch switches).
    println!("cargo:rerun-if-changed=.git/HEAD");
    println!("cargo:rerun-if-changed=.git/refs");
}