Add --disassemble flag

Dumps disassembly of the given script to STDOUT and exits immediately.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/main.rs

@@ -16,6 +16,9 @@ use crate::vm::frame::{Frame, UserFrame};
 struct Opt {
     #[structopt(name = "PATH", parse(from_os_str))]
     path: Option<PathBuf>,
+
+    #[structopt(long)]
+    disassemble: bool,
 }
 
 type Result<T = (), E = Box<dyn std::error::Error>> = std::result::Result<T, E>;
@@ -72,8 +75,11 @@ fn main() -> Result {
     exec_body.push(Inst::Push(ObjPtr::new(Int::new(0))));
     exec_body.push(Inst::Return);
 
-    //disassemble(&exec_body);
-    //return Ok(());
+    // Disassemble
+    if opt.disassemble {
+        disassemble(&exec_body);
+        return Ok(());
+    }
 
     let locals: Vec<_> = scope.keys().copied().collect();
     let main_fun: ObjPtr<_> = UserFun::new(None, vec![], locals, exec_body).into();