7500: really permit a directory whose name contains spaces

Signed-off-by: Johannes Sixt <j6t@kdbg.org>

Author: j6t

t/t7500-commit-template-squash-signoff.sh

@@ -132,7 +132,8 @@ EOF
 test_expect_success 'commit message from template with whitespace issue' '
 	echo "content galore" >>foo &&
 	git add foo &&
-	GIT_EDITOR=\""$TEST_DIRECTORY"\"/t7500/add-whitespaced-content \
+	TEST_DIRECTORY="$TEST_DIRECTORY" \
+	GIT_EDITOR="\$TEST_DIRECTORY"/t7500/add-whitespaced-content \
 	git commit --template "$TEMPLATE" &&
 	commit_msg_is "commit message"
 '