build.rs

use std::process::Command;

fn main() {
    // LATER Multiple issues with using build.rs:
    //  - It can report incorrect commit - it doesn't rerun after commit
    //    EDIT 2023-07-23 it reruns on any change, including .git
    //  - Measure how much it slows down incremental rebuilds
    //  - Any way to only use build.rs in release builds?
    // LATER consider https://docs.rs/vergen/latest/vergen/

    // Ideally we'd also save --dirty status but that often means
    // recompiling when non-code files in the repo changed.
    let describe = Command::new("git")
        .args(["describe", "--long", "--always"])
        .output()
        .unwrap()
        .stdout;
    let describe = String::from_utf8(describe).unwrap();
    let describe = describe.trim_end_matches('\n');
    // e.g. v0.1.0-109-g6a10529

    let log = Command::new("git")
        .args([
            "log",
            "-n",
            "1",
            "--pretty=format:%cd %s",
            "--date=format:%Y-%m-%d %H:%M",
        ])
        .output()
        .unwrap()
        .stdout;
    let log = String::from_utf8(log).unwrap();
    // e.g. 2021-09-09 14:17 Bigger missiles

    println!("cargo:rustc-env=GIT_VERSION={describe} {log}");
}