Allow cp multiple files at once (#6114)

* Allow cp multiple files at once

* Expand destination with expand_ndots

crates/nu-command/tests/commands/cp.rs

@@ -17,6 +17,22 @@ fn copies_a_file() {
     });
 }
 
+#[test]
+fn copies_multiple_files() {
+    Playground::setup("cp_test_1_1", |dirs, sandbox| {
+        sandbox
+            .with_files(vec![EmptyFile("a.txt"), EmptyFile("b.txt")])
+            .mkdir("dest");
+        nu!(
+            cwd: dirs.test(),
+            "cp a.txt b.txt dest",
+        );
+
+        assert!(dirs.test().join("dest/a.txt").exists());
+        assert!(dirs.test().join("dest/b.txt").exists());
+    });
+}
+
 #[test]
 fn copies_the_file_inside_directory_if_path_to_copy_is_directory() {
     Playground::setup("cp_test_2", |dirs, _| {