Use plural

Author: cruessler

gitoxide-core/src/repository/diff.rs

@@ -16,7 +16,7 @@ pub fn tree(
 
     writeln!(
         out,
-        "Diffing tree `{old_treeish}` ({old_tree_id}) -> `{new_treeish}` ({new_tree_id})"
+        "Diffing trees `{old_treeish}` ({old_tree_id}) -> `{new_treeish}` ({new_tree_id})"
     )?;
     writeln!(out)?;