include git commit SHA in --version output

CHANGELOG.md

@@ -7,8 +7,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ## Unreleased
 ### Added
 - AIFF (Audio Interchange File Format, a PCM audio format like WAV) detection to [`infer`]
+- `--version` output now includes the (short) hash of the git commit fif was built from
 ### Other
-- Refactoring - split fif into main.rs and lib.rs, moved file-related functionality (directory scanning, etc.) into
+- Refactoring - split fif into `main.rs` and `lib.rs`, moved file-related functionality (directory scanning, etc.) into
 files module, removed string module, etc.
 - Changelog "refactoring":
   - Based on the somewhat popular [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) guide, splitting the previous

build.rs

@@ -1,3 +1,5 @@
+use std::process::Command;
+
 #[allow(unreachable_code, clippy::pedantic)]
 fn main() -> Result<(), String> {
 	#[cfg(all(feature = "infer-backend", feature = "xdg-mime-backend"))]
@@ -6,5 +8,21 @@ fn main() -> Result<(), String> {
 		"fif cannot be compiled with multiple backends set - please enable only one, or use the default.",
 	));
 
+	// a more robust way of doing this would be to use vergen (https://github.com/rustyhorde/vergen), but it pulls in a
+	// whole bunch of extra dependencies (including chrono and git2), and also blocks compilation on the current MSRV.
+	// this method is less clever and robust, but it works!
+	let git = Command::new("git").args(&["rev-parse", "--short", "HEAD"]).output();
+	let hash = match git {
+		Ok(output) => String::from_utf8_lossy(&*output.stdout).into(),
+		Err(_) => {
+			// git not being present (or failing) shouldn't block compilation
+			println!("cargo:warning=Failed to retrieve git commit hash");
+			String::from("???")
+		}
+	};
+
+	println!("cargo:rustc-env=GIT_SHA={}", hash);
+	println!("cargo:rustc-rerun-if-changed=.git/HEAD");
+
 	Ok(())
 }

src/utils.rs

@@ -30,7 +30,15 @@ pub fn clap_version() -> &'static str { CLAP_VERSION.get_or_init(|| String::from
 /// Sets [`CLAP_LONG_VERSION`] to be similar to [`CLAP_VERSION`], followed by the chosen backend in parentheses (e.g.
 /// "v0.3.1 (XDG-Mime backend)"), then returns it as a String.
 pub fn clap_long_version() -> &'static str {
-	CLAP_LONG_VERSION.get_or_init(|| format!("v{} ({} backend)", VERSION.unwrap_or("???"), BACKEND).into())
+	CLAP_LONG_VERSION.get_or_init(|| {
+		format!(
+			"v{} ({} backend, commit #{})",
+			VERSION.unwrap_or("???"),
+			BACKEND,
+			option_env!("GIT_SHA").unwrap_or("???")
+		)
+		.into()
+	})
 }
 
 /// Returns the name of the target operating system with proper casing, like "Windows" or "macOS".