t1501: remove use of test_might_fail cp

The test_must_fail() family of functions (including test_might_fail())
should only be used on git commands. Replace test_might_fail() with
a compound command wrapping the old cp invocation that always returns 0.

The `test_might_fail cp` line was introduced in 466e8d5 (t1501: fix
test with split index, 2015-03-24). It is necessary because there might
exist some index files in `repo.git/sharedindex.*` and, if they exist,
we want to copy them over. However, if they don't exist, we don't want
to error out because we expect that possibility. As a result, we want to
keep the "might fail" semantics so we always return 0, even if the
underlying cp errors out.

Signed-off-by: Denton Liu <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Denton-L

t/t1501-work-tree.sh

@@ -350,7 +350,7 @@ test_expect_success 'Multi-worktree setup' '
 	mkdir work &&
 	mkdir -p repo.git/repos/foo &&
 	cp repo.git/HEAD repo.git/index repo.git/repos/foo &&
-	test_might_fail cp repo.git/sharedindex.* repo.git/repos/foo &&
+	{ cp repo.git/sharedindex.* repo.git/repos/foo || :; } &&
 	sane_unset GIT_DIR GIT_CONFIG GIT_WORK_TREE
 '