Add the git hash and commit/date to --version (#896)

Inspired by similar functionality on `wit-bindgen`

build.rs

@@ -0,0 +1,34 @@
+use std::{path::Path, process::Command};
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    commit_info();
+}
+
+fn commit_info() {
+    if !Path::new(".git").exists() {
+        return;
+    }
+    let output = match Command::new("git")
+        .arg("log")
+        .arg("-1")
+        .arg("--date=short")
+        .arg("--format=%H %h %cd")
+        .arg("--abbrev=9")
+        .output()
+    {
+        Ok(output) if output.status.success() => output,
+        _ => return,
+    };
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    let mut parts = stdout.split_whitespace();
+    let mut next = || parts.next().unwrap();
+    println!("cargo:rustc-env=CARGO_GIT_HASH={}", next());
+    println!(
+        "cargo:rustc-env=CARGO_VERSION_INFO={} ({} {})",
+        env!("CARGO_PKG_VERSION"),
+        next(),
+        next()
+    );
+}

src/bin/wasm-tools/main.rs

@@ -14,7 +14,7 @@ macro_rules! subcommands {
         )*
 
         #[derive(Parser)]
-        #[clap(version)]
+        #[clap(version = version())]
         #[allow(non_camel_case_types)]
         enum WasmTools {
             $(
@@ -72,6 +72,11 @@ fn main() -> ExitCode {
     ExitCode::FAILURE
 }
 
+/// If CARGO_VERSION_INFO is set, use it, otherwise use CARGO_PKG_VERSION.
+fn version() -> &'static str {
+    option_env!("CARGO_VERSION_INFO").unwrap_or(env!("CARGO_PKG_VERSION"))
+}
+
 #[test]
 fn verify_cli() {
     use clap::CommandFactory;