A broken here-document was not caught because end of file is taken by
an implicit end of the here document (POSIX does not seem to say it is
an error to lack the delimiter), and everything in the test just turned
into a single "cat into a file".
Noticed-by: NKacper Kornet <draenog@pld-linux.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>