t1300: demonstrate that CamelCased aliases regressed

It is totally legitimate to add CamelCased aliases, but due to the way
config keys are compared, the case does not matter.

Except that now it does: the alias name is expected to be all
lower-case. This is a regression introduced by a9bcf6586d (alias: use
the early config machinery to expand aliases, 2017-06-14).

Noticed by Alejandro Pauly, diagnosed by Kevin Willford.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1300-repo-config.sh

@@ -1075,6 +1075,13 @@ test_expect_success 'git -c works with aliases of builtins' '
 	test_cmp expect actual
 '
 
+test_expect_failure 'aliases can be CamelCased' '
+	test_config alias.CamelCased "rev-parse HEAD" &&
+	git CamelCased >out &&
+	git rev-parse HEAD >expect &&
+	test_cmp expect out
+'
+
 test_expect_success 'git -c does not split values on equals' '
 	echo "value with = in it" >expect &&
 	git -c core.foo="value with = in it" config core.foo >actual &&