Add test of rename with no changes

A tree to index rename with no changes was getting erased by
the iteration routine (if the routine actually loaded the data
for the unmodified file).  This invokes the code path that was
previously messing up the diff and iterates twice to make sure
that the iteration process itself doesn't modify the data.

tests-clar/diff/rename.c

@@ -899,6 +899,7 @@ void test_diff_rename__rejected_match_can_match_others(void)
 	cl_git_pass(
 		git_diff_foreach(diff, test_names_expected, NULL, NULL, &expect));
 
+	git_diff_list_free(diff);
 	git_tree_free(tree);
 	git_index_free(index);
 	git_reference_free(head);
@@ -913,6 +914,7 @@ void test_diff_rename__case_changes_are_split(void)
 	git_tree *tree;
 	git_diff_list *diff = NULL;
 	diff_expects exp;
+	git_diff_find_options opts = GIT_DIFF_FIND_OPTIONS_INIT;
 
 	cl_git_pass(git_repository_index(&index, g_repo));
 
@@ -934,6 +936,61 @@ void test_diff_rename__case_changes_are_split(void)
 	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_DELETED]);
 	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_ADDED]);
 
+	opts.flags = GIT_DIFF_FIND_ALL;
+	cl_git_pass(git_diff_find_similar(diff, &opts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(1, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+
+	git_diff_list_free(diff);
 	git_index_free(index);
 }
 
+void test_diff_rename__unmodified_can_be_renamed(void)
+{
+	git_index *index;
+	git_tree *tree;
+	git_diff_list *diff = NULL;
+	diff_expects exp;
+	git_diff_options diffopts = GIT_DIFF_OPTIONS_INIT;
+	git_diff_find_options opts = GIT_DIFF_FIND_OPTIONS_INIT;
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+	cl_git_pass(
+		git_revparse_single((git_object **)&tree, g_repo, "HEAD^{tree}"));
+
+	cl_git_pass(p_rename("renames/ikeepsix.txt", "renames/ikeepsix2.txt"));
+
+	cl_git_pass(git_index_remove_bypath(index, "ikeepsix.txt"));
+	cl_git_pass(git_index_add_bypath(index, "ikeepsix2.txt"));
+	cl_git_pass(git_index_write(index));
+
+	cl_git_pass(git_diff_tree_to_index(&diff, g_repo, tree, index, &diffopts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(2, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_DELETED]);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_ADDED]);
+
+	opts.flags = GIT_DIFF_FIND_ALL;
+	cl_git_pass(git_diff_find_similar(diff, &opts));
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(1, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+
+	memset(&exp, 0, sizeof(exp));
+	cl_git_pass(git_diff_foreach(
+		diff, diff_file_cb, diff_hunk_cb, diff_line_cb, &exp));
+	cl_assert_equal_i(1, exp.files);
+	cl_assert_equal_i(1, exp.file_status[GIT_DELTA_RENAMED]);
+
+	git_diff_list_free(diff);
+}