mailmap: do not downcase mailmap entries

The email addresses in the records read from the .mailmap file are
downcased very early, and then used to match against e-mail
addresses in the input.  Because we do use case insensitive version
of string list to manage these entries, there is no need to do this,
and worse yet, downcasing the rewritten/canonical e-mail read from
the .mailmap file loses information.

Stop doing that, and also make the string list used to keep multiple
names for an mailmap entry case insensitive (the code that uses the
list, lookup_prefix(), expects a case insensitive match).

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

mailmap.c

@@ -51,14 +51,6 @@ static void add_mapping(struct string_list *map,
 {
 	struct mailmap_entry *me;
 	int index;
-	char *p;
-
-	if (old_email)
-		for (p = old_email; *p; p++)
-			*p = tolower(*p);
-	if (new_email)
-		for (p = new_email; *p; p++)
-			*p = tolower(*p);
 
 	if (old_email == NULL) {
 		old_email = new_email;
@@ -68,13 +60,17 @@ static void add_mapping(struct string_list *map,
 	if ((index = string_list_find_insert_index(map, old_email, 1)) < 0) {
 		/* mailmap entry exists, invert index value */
 		index = -1 - index;
+		me = (struct mailmap_entry *)map->items[index].util;
 	} else {
 		/* create mailmap entry */
-		struct string_list_item *item = string_list_insert_at_index(map, index, old_email);
-		item->util = xcalloc(1, sizeof(struct mailmap_entry));
-		((struct mailmap_entry *)item->util)->namemap.strdup_strings = 1;
+		struct string_list_item *item;
+
+		item = string_list_insert_at_index(map, index, old_email);
+		me = xcalloc(1, sizeof(struct mailmap_entry));
+		me->namemap.strdup_strings = 1;
+		me->namemap.cmp = strcasecmp;
+		item->util = me;
 	}
-	me = (struct mailmap_entry *)map->items[index].util;
 
 	if (old_name == NULL) {
 		debug_mm("mailmap: adding (simple) entry for %s at index %d\n", old_email, index);

t/t4203-mailmap.sh

@@ -256,7 +256,7 @@ test_expect_success 'single-character name' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'preserve canonical email case' '
+test_expect_success 'preserve canonical email case' '
 	echo "     1	A U Thor <AUTHOR@example.com>" >expect &&
 	echo "     1	nick1 <bugs@company.xx>" >>expect &&
 	echo "<AUTHOR@example.com> <author@example.com>" >.mailmap &&