Create miscapitialised dirs for case-sensitive filesystems

We need these directories to exist so cl_git_mkfile() can create the
files we ask it to.

tests/index/tests.c

@@ -338,6 +338,10 @@ void test_index_tests__add_invalid_filename(void)
 	cl_git_pass(git_repository_init(&repo, "./invalid", 0));
 	cl_must_pass(p_mkdir("./invalid/subdir", 0777));
 
+	/* cl_git_mkfile() needs the dir to exist */
+	cl_must_pass(p_mkdir("./invalid/.GIT", 0777));
+	cl_must_pass(p_mkdir("./invalid/.GiT", 0777));
+
 	add_invalid_filename(repo, ".git/hello");
 	add_invalid_filename(repo, ".GIT/hello");
 	add_invalid_filename(repo, ".GiT/hello");