cp: correct --verbose --parents output for files

This commit corrects the behavior of `cp --parents --verbose` when the
source path is a file so that it prints the copied ancestor
directories. For example,

    $ mkdir -p a/b d
    $ touch a/b/c
    $ cp --verbose --parents a/b/c d
    a -> d/a
    a/b -> d/a/b
    'a/b/c' -> 'd/a/b/c'

Fixes uutils#3332.

src/uu/cp/src/cp.rs

@@ -1311,6 +1311,47 @@ fn file_or_link_exists(path: &Path) -> bool {
     path.symlink_metadata().is_ok()
 }
 
+/// Zip the ancestors of a source path and destination path.
+///
+/// # Examples
+///
+/// ```rust,ignore
+/// let actual = aligned_ancestors(&Path::new("a/b/c"), &Path::new("d/a/b/c"));
+/// let expected = vec![
+///     (Path::new("a"), Path::new("d/a")),
+///     (Path::new("a/b"), Path::new("d/a/b")),
+/// ];
+/// assert_eq!(actual, expected);
+/// ```
+fn aligned_ancestors<'a>(source: &'a Path, dest: &'a Path) -> Vec<(&'a Path, &'a Path)> {
+    // Collect the ancestors of each. For example, if `source` is
+    // "a/b/c", then the ancestors are "a/b/c", "a/b", "a/", and "".
+    let source_ancestors: Vec<&Path> = source.ancestors().collect();
+    let dest_ancestors: Vec<&Path> = dest.ancestors().collect();
+
+    // For this particular application, we don't care about the null
+    // path "" and we don't care about the full path (e.g. "a/b/c"),
+    // so we exclude those.
+    let n = source_ancestors.len();
+    let source_ancestors = &source_ancestors[1..n - 1];
+
+    // Get the matching number of elements from the ancestors of the
+    // destination path (for example, get "d/a" and "d/a/b").
+    let k = source_ancestors.len();
+    let dest_ancestors = &dest_ancestors[1..1 + k];
+
+    // Now we have two slices of the same length, so we zip them.
+    let mut result = vec![];
+    for (x, y) in source_ancestors
+        .iter()
+        .rev()
+        .zip(dest_ancestors.iter().rev())
+    {
+        result.push((*x, *y));
+    }
+    result
+}
+
 /// Copy the a file from `source` to `dest`. `source` will be dereferenced if
 /// `options.dereference` is set to true. `dest` will be dereferenced only if
 /// the source was not a symlink.
@@ -1370,9 +1411,33 @@ fn copy_file(
         if let Some(pb) = progress_bar {
             // Suspend (hide) the progress bar so the println won't overlap with the progress bar.
             pb.suspend(|| {
+                if options.parents {
+                    // For example, if copying file `a/b/c` and its parents
+                    // to directory `d/`, then print
+                    //
+                    //     a -> d/a
+                    //     a/b -> d/a/b
+                    //
+                    for (x, y) in aligned_ancestors(source, dest) {
+                        println!("{} -> {}", x.display(), y.display());
+                    }
+                }
+
                 println!("{}", context_for(source, dest));
             });
         } else {
+            if options.parents {
+                // For example, if copying file `a/b/c` and its parents
+                // to directory `d/`, then print
+                //
+                //     a -> d/a
+                //     a/b -> d/a/b
+                //
+                for (x, y) in aligned_ancestors(source, dest) {
+                    println!("{} -> {}", x.display(), y.display());
+                }
+            }
+
             println!("{}", context_for(source, dest));
         }
     }
@@ -1671,15 +1736,29 @@ fn disk_usage_directory(p: &Path) -> io::Result<u64> {
     Ok(total)
 }
 
-#[test]
-fn test_cp_localize_to_target() {
-    assert!(
-        localize_to_target(
-            Path::new("a/source/"),
-            Path::new("a/source/c.txt"),
-            Path::new("target/")
-        )
-        .unwrap()
-            == Path::new("target/c.txt")
-    );
+#[cfg(test)]
+mod tests {
+
+    use crate::{aligned_ancestors, localize_to_target};
+    use std::path::Path;
+
+    #[test]
+    fn test_cp_localize_to_target() {
+        let root = Path::new("a/source/");
+        let source = Path::new("a/source/c.txt");
+        let target = Path::new("target/");
+        let actual = localize_to_target(root, source, target).unwrap();
+        let expected = Path::new("target/c.txt");
+        assert_eq!(actual, expected);
+    }
+
+    #[test]
+    fn test_aligned_ancestors() {
+        let actual = aligned_ancestors(&Path::new("a/b/c"), &Path::new("d/a/b/c"));
+        let expected = vec![
+            (Path::new("a"), Path::new("d/a")),
+            (Path::new("a/b"), Path::new("d/a/b")),
+        ];
+        assert_eq!(actual, expected);
+    }
 }

tests/by-util/test_cp.rs

@@ -26,7 +26,6 @@ use std::fs as std_fs;
 use std::thread::sleep;
 #[cfg(not(target_os = "freebsd"))]
 use std::time::Duration;
-use uucore::display::Quotable;
 
 static TEST_EXISTING_FILE: &str = "existing_file.txt";
 static TEST_HELLO_WORLD_SOURCE: &str = "hello_world.txt";
@@ -2054,46 +2053,37 @@ fn test_cp_parents_2_dirs() {
 }
 
 #[test]
-#[ignore = "issue #3332"]
 fn test_cp_parents_2() {
     let (at, mut ucmd) = at_and_ucmd!();
     at.mkdir_all("a/b");
     at.touch("a/b/c");
     at.mkdir("d");
-    ucmd.args(&["--verbose", "-a", "--parents", "a/b/c", "d"])
+    #[cfg(not(windows))]
+    let expected_stdout = "a -> d/a\na/b -> d/a/b\n'a/b/c' -> 'd/a/b/c'\n";
+    #[cfg(windows)]
+    let expected_stdout = "a -> d\\a\na/b -> d\\a/b\n'a/b/c' -> 'd\\a/b/c'\n";
+    ucmd.args(&["--verbose", "--parents", "a/b/c", "d"])
         .succeeds()
-        .stdout_is(format!(
-            "{} -> {}\n{} -> {}\n{} -> {}\n",
-            "a",
-            path_concat!("d", "a"),
-            path_concat!("a", "b"),
-            path_concat!("d", "a", "b"),
-            path_concat!("a", "b", "c").quote(),
-            path_concat!("d", "a", "b", "c").quote()
-        ));
+        .stdout_only(expected_stdout);
     assert!(at.file_exists("d/a/b/c"));
 }
 
 #[test]
-#[ignore = "issue #3332"]
 fn test_cp_parents_2_link() {
     let (at, mut ucmd) = at_and_ucmd!();
     at.mkdir_all("a/b");
     at.touch("a/b/c");
     at.mkdir("d");
     at.relative_symlink_file("b", "a/link");
-    ucmd.args(&["--verbose", "-a", "--parents", "a/link/c", "d"])
+    #[cfg(not(windows))]
+    let expected_stdout = "a -> d/a\na/link -> d/a/link\n'a/link/c' -> 'd/a/link/c'\n";
+    #[cfg(windows)]
+    let expected_stdout = "a -> d\\a\na/link -> d\\a/link\n'a/link/c' -> 'd\\a/link/c'\n";
+    ucmd.args(&["--verbose", "--parents", "a/link/c", "d"])
         .succeeds()
-        .stdout_is(format!(
-            "{} -> {}\n{} -> {}\n{} -> {}\n",
-            "a",
-            path_concat!("d", "a"),
-            path_concat!("a", "link"),
-            path_concat!("d", "a", "link"),
-            path_concat!("a", "link", "c").quote(),
-            path_concat!("d", "a", "link", "c").quote()
-        ));
-    assert!(at.dir_exists("d/a/link") && !at.symlink_exists("d/a/link"));
+        .stdout_only(expected_stdout);
+    assert!(at.dir_exists("d/a/link"));
+    assert!(!at.symlink_exists("d/a/link"));
     assert!(at.file_exists("d/a/link/c"));
 }