mv: fix subdir detection

src/uu/mv/src/mv.rs

@@ -358,29 +358,15 @@ fn handle_two_paths(source: &Path, target: &Path, opts: &Options) -> UResult<()>
             } else {
                 Err(MvError::DirectoryToNonDirectory(target.quote().to_string()).into())
             }
-        } else {
         // Check that source & target do not contain same subdir/dir when both exist
         // mkdir dir1/dir2; mv dir1 dir1/dir2
-            let target_contains_itself = target
-                .as_os_str()
-                .to_str()
-                .ok_or("not a valid unicode string")
-                .and_then(|t| {
-                    source
-                        .as_os_str()
-                        .to_str()
-                        .ok_or("not a valid unicode string")
-                        .map(|s| t.contains(s))
-                })
-                .unwrap();
-
-            if target_contains_itself {
-                return Err(MvError::SelfTargetSubdirectory(
+        } else if target.starts_with(source) {
+            Err(MvError::SelfTargetSubdirectory(
                 source.display().to_string(),
                 target.display().to_string(),
             )
-                .into());
-            }
+            .into())
+        } else {
             move_files_into_dir(&[source.to_path_buf()], target, opts)
         }
     } else if target.exists() && source.is_dir() {

tests/by-util/test_mv.rs

@@ -1455,6 +1455,20 @@ fn test_mv_directory_into_subdirectory_of_itself_fails() {
         );
 }
 
+#[test]
+fn test_mv_dir_into_dir_with_source_name_a_prefix_of_target_name() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    let source = "test";
+    let target = "test2";
+
+    at.mkdir(source);
+    at.mkdir(target);
+
+    ucmd.arg(source).arg(target).succeeds().no_output();
+
+    assert!(at.dir_exists(&format!("{target}/{source}")));
+}
+
 #[test]
 fn test_mv_file_into_dir_where_both_are_files() {
     let scene = TestScenario::new(util_name!());