add git hash

build.rs

@@ -0,0 +1,7 @@
+use std::process::Command;
+fn main() {
+    // note: add error checking yourself.
+    let output = Command::new("git").args(&["rev-parse", "HEAD"]).output().unwrap();
+    let git_hash = String::from_utf8(output.stdout).unwrap();
+    println!("cargo:rustc-env=GIT_HASH={}", git_hash);
+}

src/main.rs

@@ -14,14 +14,15 @@ use argparse::{ArgumentParser, StoreTrue, Store};
 use rust_util::*;
 
 const VERSION: &str = env!("CARGO_PKG_VERSION");
+const GIT_HASH: &str = env!("GIT_HASH");
 
 fn print_version() {
-    print!(r#"prettyjson {}
+    print!(r#"prettyjson {} - {}
 Copyright (C) 2019 Hatter Jiang.
 License MIT <https://opensource.org/licenses/MIT>
 
 Written by Hatter Jiang
-"#, VERSION);
+"#, VERSION, &GIT_HASH[0..7]);
 }
 
 fn read_to_string(read: &mut Read) -> XResult<String> {