tests: fix syntax error in "Use advise() for hints" test

Change the test introduced in the "Use advise() for hints" patch by
Jonathan Nieder not to use '' for quotes inside '' delimited code. It
ended up introducing a file called <paths> to the main git repository.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3507-cherry-pick-conflict.sh

@@ -38,7 +38,7 @@ test_expect_success 'failed cherry-pick does not advance HEAD' '
 	test "$head" = "$newhead"
 '
 
-test_expect_success 'advice from failed cherry-pick' '
+test_expect_success 'advice from failed cherry-pick' "
 	git checkout -f initial^0 &&
 	git read-tree -u --reset HEAD &&
 	git clean -d -f -f -q -x &&
@@ -46,17 +46,17 @@ test_expect_success 'advice from failed cherry-pick' '
 	git update-index --refresh &&
 	git diff-index --exit-code HEAD &&
 
-	picked=$(git rev-parse --short picked) &&
+	picked=\$(git rev-parse --short picked) &&
 	cat <<-EOF >expected &&
-	error: could not apply $picked... picked
+	error: could not apply \$picked... picked
 	hint: after resolving the conflicts, mark the corrected paths
 	hint: with 'git add <paths>' or 'git rm <paths>'
-	hint: and commit the result with 'git commit -c $picked'
+	hint: and commit the result with 'git commit -c \$picked'
 	EOF
 	test_must_fail git cherry-pick picked 2>actual &&
 
 	test_cmp expected actual
-'
+"
 
 test_expect_success 'failed cherry-pick produces dirty index' '