Add nonterminal with function

For making tab completion work properly

schala-repl/src/repl/command_tree.rs

@@ -13,6 +13,7 @@ pub enum CommandTree {
     name: String,
     children: Vec<CommandTree>,
     help_msg: Option<String>,
+    function: Option<BoxedCommandFunction>,
   },
   Top(Vec<CommandTree>),
 }
@@ -31,6 +32,16 @@ impl CommandTree {
       name: s.to_string(),
       help_msg: help.map(|x| x.to_string()),
       children,
+      function: None,
+    }
+  }
+
+  pub fn nonterm_with_function(s: &str, help: Option<&str>, children: Vec<CommandTree>, func: BoxedCommandFunction) -> CommandTree {
+    CommandTree::NonTerminal {
+      name: s.to_string(),
+      help_msg: help.map(|x| x.to_string()),
+      children,
+      function: Some(func),
     }
   }