chore: checkpoint before Python removal

vendor/pest_derive/examples/help-menu.rs

@@ -0,0 +1,28 @@
+#[macro_use]
+extern crate pest_derive;
+extern crate pest;
+
+use pest::Parser;
+
+#[derive(Parser)]
+#[grammar = "../examples/help-menu.pest"]
+struct HelpMenuGrammar;
+
+const INPUT: &str = r"cli help
+cli positional-command <required-single-argument> [optional-single-argument]
+cli [choice | of | one | or | none | of | these | options]
+cli <choice | of | one | of | these | options>
+cli [nesting | <is | ok>]
+";
+
+fn main() {
+    HelpMenuGrammar::parse(Rule::HelpMenu, INPUT)
+        .expect("Error parsing file")
+        .next()
+        .expect("Infallible")
+        .into_inner()
+        .filter(|pair| Rule::Command == pair.as_rule())
+        .for_each(|pair| {
+            println!("{:#?}", pair);
+        });
+}