alias: compare alias name *case-insensitively*

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

Therefore, we must compare the alias name insensitively to the config
keys.

This fixes a regression introduced by a9bcf6586d (alias: use
the early config machinery to expand aliases, 2017-06-14).

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

alias.c

@@ -10,7 +10,7 @@ static int config_alias_cb(const char *key, const char *value, void *d)
 	struct config_alias_data *data = d;
 	const char *p;
 
-	if (skip_prefix(key, "alias.", &p) && !strcmp(p, data->alias))
+	if (skip_prefix(key, "alias.", &p) && !strcasecmp(p, data->alias))
 		return git_config_string((const char **)&data->v, key, value);
 
 	return 0;

t/t1300-repo-config.sh

@@ -1075,7 +1075,7 @@ test_expect_success 'git -c works with aliases of builtins' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'aliases can be CamelCased' '
+test_expect_success 'aliases can be CamelCased' '
 	test_config alias.CamelCased "rev-parse HEAD" &&
 	git CamelCased >out &&
 	git rev-parse HEAD >expect &&