allow including extra info in --version output

src/clap.rs

@@ -2,9 +2,23 @@
 
 use clap::Parser;
 
+/// Returns the current version of the crate with extra info if supplied
+///
+/// Set the environment variable `CONDUIT_VERSION_EXTRA` to any UTF-8 string to
+/// include it in parenthesis after the SemVer version. A common value are git
+/// commit hashes.
+fn version() -> String {
+    let cargo_pkg_version = env!("CARGO_PKG_VERSION");
+
+    match option_env!("CONDUIT_VERSION_EXTRA") {
+        Some(x) => format!("{} ({})", cargo_pkg_version, x),
+        None => cargo_pkg_version.to_owned(),
+    }
+}
+
 /// Command line arguments
 #[derive(Parser)]
-#[clap(about, version)]
+#[clap(about, version = version())]
 pub struct Args {}
 
 /// Parse command line arguments into structured data