add build.rs to export GIT_HASH for us

build.rs

@@ -0,0 +1,24 @@
+use std::{env, process::Command};
+
+fn main() {
+    // Get the current directory of the project
+    let project_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+
+    let output = Command::new("git")
+        .arg("rev-parse")
+        .arg("--short")
+        .arg("HEAD")
+        .current_dir(&project_dir)
+        .output()
+        .expect("Failed to execute git command");
+
+    if output.status.success() {
+        let commit_hash = String::from_utf8(output.stdout).expect("Git output is not valid UTF-8");
+
+        // Export the commit hash as a build-time constant
+        println!("cargo:rustc-env=GIT_HASH={}", commit_hash);
+    } else {
+        // Handle the case where the git command failed
+        eprintln!("Failed to get Git commit hash");
+    }
+}