cp: correctly copy ancestor dirs in --parents mode

Fix a bug where `cp` failed to copy ancestor directories when using
the `--parents` option. For example, before this commit:

    $ mkdir -p a/b/c d
    $ cp --parents a/b/c d
    $ find d
    d
    d/c

After this commit

    $ mkdir -p a/b/c d
    $ cp --parents a/b/c d
    $ find d
    d
    d/a
    d/a/b
    d/a/b/c

This commit also adds the correct messages for `--verbose` mode:

    $ cp -r --parents --verbose a/b/c d
    a -> d/a
    a/b -> d/a/b
    'a/b/c' -> 'd/a/b/c'

Fixes #3332.

src/uu/cp/src/copydir.rs

@@ -303,6 +303,27 @@ pub(crate) fn copy_directory(
         .into());
     }
 
+    // If in `--parents` mode, create all the necessary ancestor directories.
+    //
+    // For example, if the command is `cp --parents a/b/c d`, that
+    // means we need to copy the two ancestor directories first:
+    //
+    // a -> d/a
+    // a/b -> d/a/b
+    //
+    let tmp = if options.parents {
+        if let Some(parent) = root.parent() {
+            let new_target = target.join(parent);
+            std::fs::create_dir_all(&new_target)?;
+            new_target
+        } else {
+            target.to_path_buf()
+        }
+    } else {
+        target.to_path_buf()
+    };
+    let target = tmp.as_path();
+
     let mut hard_links: Vec<(String, u64)> = vec![];
     let preserve_hard_links = options.preserve_hard_links();
 

tests/by-util/test_cp.rs

@@ -1999,6 +1999,19 @@ fn test_copy_same_symlink_no_dereference_dangling() {
     ucmd.args(&["-d", "a", "b"]).succeeds();
 }
 
+#[cfg(not(windows))]
+#[test]
+fn test_cp_parents_2_dirs() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.mkdir_all("a/b/c");
+    at.mkdir("d");
+    ucmd.args(&["-a", "--parents", "a/b/c", "d"])
+        .succeeds()
+        .no_stderr()
+        .no_stdout();
+    assert!(at.dir_exists("d/a/b/c"));
+}
+
 #[test]
 #[ignore = "issue #3332"]
 fn test_cp_parents_2() {