chore: checkpoint before Python removal

vendor/clap/examples/derive_ref/augment_args.rs

@@ -0,0 +1,27 @@
+use clap::{Args, Command, FromArgMatches as _, arg};
+
+#[derive(Args, Debug)]
+struct DerivedArgs {
+    #[arg(short, long)]
+    derived: bool,
+}
+
+fn main() {
+    let cli = Command::new("CLI").arg(arg!(-b - -built).action(clap::ArgAction::SetTrue));
+    // Augment built args with derived args
+    let cli = DerivedArgs::augment_args(cli);
+
+    let matches = cli.get_matches();
+    println!("Value of built: {:?}", matches.get_flag("built"));
+    println!(
+        "Value of derived via ArgMatches: {:?}",
+        matches.get_flag("derived")
+    );
+
+    // Since DerivedArgs implements FromArgMatches, we can extract it from the unstructured ArgMatches.
+    // This is the main benefit of using derived arguments.
+    let derived_matches = DerivedArgs::from_arg_matches(&matches)
+        .map_err(|err| err.exit())
+        .unwrap();
+    println!("Value of derived: {derived_matches:#?}");
+}