cp: fix update prompting (uutils#7668)

* added logic to check if we are updating the file and the destination is newer, to skip copying

* corrected logic to handle cp update

* - added test case that mocks the issue described in uutils#7660
- adjusted conditions to satisfy clippy

* typo

* Update src/uu/cp/src/cp.rs

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

* Update tests/by-util/test_cp.rs

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

---------

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

Author: 2 people

src/uu/cp/src/cp.rs

@@ -1828,6 +1828,13 @@ fn handle_existing_dest(
         return Err(format!("{} and {} are the same file", source.quote(), dest.quote()).into());
     }
 
+    if options.update == UpdateMode::ReplaceNone {
+        if options.debug {
+            println!("skipped {}", dest.quote());
+        }
+        return Err(Error::Skipped(false));
+    }
+
     if options.update != UpdateMode::ReplaceIfOlder {
         options.overwrite.verify(dest, options.debug)?;
     }

tests/by-util/test_cp.rs

@@ -6167,3 +6167,20 @@ fn test_cp_update_older_interactive_prompt_no() {
         .fails()
         .stdout_is("cp: overwrite 'old'? ");
 }
+
+#[test]
+fn test_cp_update_none_interactive_prompt_no() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let old_file = "old";
+    let new_file = "new";
+
+    at.write(old_file, "old content");
+    at.write(new_file, "new content");
+
+    ucmd.args(&["-i", "--update=none", new_file, old_file])
+        .succeeds()
+        .no_output();
+
+    assert_eq!(at.read(old_file), "old content");
+    assert_eq!(at.read(new_file), "new content");
+}