Fix review issues

Replace tabs with spaces, mention usage for borrowing, add disadvantage
(code indentation increase).

idioms/clone-to-closure.md

@@ -3,24 +3,42 @@
 ## Description
 
 By default, closures capture their environment by borrowing. Or you can use `move`-closure
-to move environment. However, often you want to give copy of some data to closure.
+to move environment. However, often you want to give copy of some data to closure, pass it
+by reference, or perform some other transformation.
+
 Use variable rebinding in separate scope for that.
 
 
 ## Example
 
+Use
+
 ```rust
-let mut num = Rc::new(5);
+let num1 = Rc::new(1);
+let num2 = Rc::new(2);
+let num3 = Rc::new(3);
 let closure = {
-	let num = num.clone();
-	move || {
-		*num + 10
-	}
+    // `num1` is moved
+    let num2 = num2.clone();  // `num2` is cloned
+    let num3 = num3.as_ref();  // `num3` is borrowed
+    move || {
+        *num1 + *num2 + *num3;
+    }
 };
+```
 
-// Instead of
-let num_copy = num.clone();
-let closure = move || { *num_copy + 10 };
+instead of
+
+```rust
+let num1 = Rc::new(1);
+let num2 = Rc::new(2);
+let num3 = Rc::new(3);
+
+let num2_cloned = num2.clone();
+let num3_borrowed = num3.as_ref();
+let closure = move || {
+	*num1 + *num2_cloned + *num3_borrowed;
+};
 ```
 
 
@@ -31,3 +49,8 @@ and they will be dropped immediately even if they are not consumed by closure.
 
 Closure uses same variable names as surrounding code whether data are copied or moved.
 
+
+## Disadvantages
+
+Additional indentation of closure body.
+