Update Exercises Directory Names to Reflect Order

exercises/06_move_semantics/move_semantics4.rs

@@ -0,0 +1,29 @@
+// move_semantics4.rs
+//
+// Refactor this code so that instead of passing `vec0` into the `fill_vec`
+// function, the Vector gets created in the function itself and passed back to
+// the main function.
+//
+// Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand
+// for a hint.
+
+// I AM NOT DONE
+
+#[test]
+fn main() {
+    let vec0 = vec![22, 44, 66];
+
+    let mut vec1 = fill_vec(vec0);
+
+    assert_eq!(vec1, vec![22, 44, 66, 88]);
+}
+
+// `fill_vec()` no longer takes `vec: Vec<i32>` as argument - don't change this!
+fn fill_vec() -> Vec<i32> {
+    // Instead, let's create and fill the Vec in here - how do you do that?
+    let mut vec = vec;
+
+    vec.push(88);
+
+    vec
+}