a little more complexity for diff tests (#470)

Author: Byron

git-repository/tests/fixtures/generated-archives/make_diff_repo.tar.xz

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:2123aa9e3fd85166d35c02c59ce8f0e8aaa3631c3dd4e43468f98d26cddf049c
-size 11128
+oid sha256:a057f8e02b4fa2743d74c84a68ace9ce2c3a051527afa8d9a5cb671b48e36868
+size 11272

git-repository/tests/fixtures/make_diff_repo.sh

@@ -5,13 +5,14 @@ git init -q
 
 git checkout -b main
 mkdir dir
-touch a b dir/c
+touch a b dir/c d
 git add .
 git commit -q -m c1
 
 echo a >> a
 echo b >> b
 echo dir/c >> dir/c
+echo d >> d
 git commit -q -am c2
 
 echo a1 >> a

git-repository/tests/object/tree.rs

@@ -52,7 +52,7 @@ mod diff {
         );
         let to = tree_named(&repo, ":/c1");
 
-        let mut expected = vec!["a", "b", "c"];
+        let mut expected = vec!["a", "b", "c", "d"];
         from.changes()
             .track_filename()
             .for_each_to_obtain_tree(&to, |change| -> Result<_, Infallible> {
@@ -62,7 +62,7 @@ mod diff {
             .unwrap();
         assert_eq!(expected, Vec::<&str>::new(), "all paths should have been seen");
 
-        let mut expected = vec!["a", "b", "dir/c"];
+        let mut expected = vec!["a", "b", "dir/c", "d"];
         from.changes()
             .track_path()
             .for_each_to_obtain_tree(&to, |change| -> Result<_, Infallible> {