Return error when moving a source directory to a target directory which contains a subdirectory with the same name as the source (#6284)

Fixes #6275

Signed-off-by: nibon7 <nibon7@163.com>

crates/nu-command/src/filesystem/mv.rs

@@ -120,6 +120,21 @@ impl Command for Mv {
             ));
         }
 
+        if source.is_dir() && destination.is_dir() {
+            if let Some(name) = source.file_name() {
+                let dst = destination.join(name);
+                if dst.is_dir() {
+                    return Err(ShellError::GenericError(
+                        format!("Can't move {:?} to {:?}", source, dst),
+                        "Directory not empty".into(),
+                        Some(spanned_destination.span),
+                        None,
+                        Vec::new(),
+                    ));
+                }
+            }
+        }
+
         let some_if_source_is_destination = sources
             .iter()
             .find(|f| matches!(f, Ok(f) if destination.starts_with(f)));