tests: rebase::submodule: verify initialization method calls

Some return codes for functions which may fail are not being checked in
`test_rebase_submodule__initialize`. This may lead us to not notice
errors when initializing the environment and would possibly result in
either memory corruption or segfaults as soon as any of the
initialization steps fails. Fix this by wrapping these function calls
into `cl_git_pass`.

tests/rebase/submodule.c

@@ -28,25 +28,25 @@ void test_rebase_submodule__initialize(void)
 
 	rewrite_gitmodules(git_repository_workdir(repo));
 
-	git_submodule_set_url(repo, "my-submodule", git_repository_path(repo));
+	cl_git_pass(git_submodule_set_url(repo, "my-submodule", git_repository_path(repo)));
 
 	/* We have to commit the rewritten .gitmodules file */
-	git_repository_index(&index, repo);
-	git_index_add_bypath(index, ".gitmodules");
-	git_index_write_tree(&tree_oid, index);
-	git_index_free(index);
+	cl_git_pass(git_repository_index(&index, repo));
+	cl_git_pass(git_index_add_bypath(index, ".gitmodules"));
+	cl_git_pass(git_index_write_tree(&tree_oid, index));
 
 	cl_git_pass(git_tree_lookup(&tree, repo, &tree_oid));
 
-	git_repository_head(&master_ref, repo);
+	cl_git_pass(git_repository_head(&master_ref, repo));
 	cl_git_pass(git_commit_lookup(&parent, repo, git_reference_target(master_ref)));
 
 	cl_git_pass(git_commit_create_v(&commit_id, repo, git_reference_name(master_ref), signature, signature, NULL, "Fixup .gitmodules", tree, 1, parent));
 
 	/* And a final reset, for good measure */
-	git_object_lookup(&obj, repo, &commit_id, GIT_OBJ_COMMIT);
+	cl_git_pass(git_object_lookup(&obj, repo, &commit_id, GIT_OBJ_COMMIT));
 	cl_git_pass(git_reset(repo, obj, GIT_RESET_HARD, &opts));
 
+	git_index_free(index);
 	git_object_free(obj);
 	git_commit_free(parent);
 	git_reference_free(master_ref);