t5605: fix test for cloning from a different user

This test currently passes, but for the wrong reason.  The
repo_is_hardlinked function expects a .git directory or a bare
repository and currently fails because it cannot find the objects
directory.

One solution is to use the --bare argument, but then --show-toplevel
won't work.  We could change that, but there's no need to, so just add
the missing .git directory.

In addition, use the built-in negation functionality of test_grep to
avoid mishandling real errors (such as a missing file) and, as a final
fix, remove the extra newline.

Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: bk2204

t/t5605-clone-local.sh

@@ -156,11 +156,10 @@ test_expect_success 'cloning a local path with --no-local does not hardlink' '
 test_expect_success 'cloning a local path with --no-local from a different user succeeds' '
 	git clone --upload-pack="GIT_TEST_ASSUME_DIFFERENT_OWNER=true git-upload-pack" \
 		--no-local a nonlocal-otheruser 2>err &&
-	! repo_is_hardlinked nonlocal-otheruser &&
+	! repo_is_hardlinked nonlocal-otheruser/.git &&
 	# Verify that this is a git repository.
 	git -C nonlocal-otheruser rev-parse --show-toplevel &&
-	! test_grep "detected dubious ownership" err
-
+	test_grep ! "detected dubious ownership" err
 '
 
 test_expect_success 'cloning locally respects "-u" for fetching refs' '