tests-subrepo-git: use "f" to dump pwned.txt, for portability Rather than sometimes using a complicated shell construct to dump pwned.txt (if it wasn't expected to exist, but might, if something were broken) or just cat (if it was expected to exist), just use the "f" utility, which will be consistent in its behavior across different platforms. Also make sure that *something* gets put into pwned.txt, even if we ended up typoing the message variable.