fix implicit listing of Maildir INBOX under Path

commit acd6b4b0 ("simplify/fix recursive maildir listing") argued that
listing INBOX when it is encountered while listing Path would be
unnecessary, as the caller would list it separately anyway if requested.
however, it is actually documented that Patterns will implicitly match
INBOX nested into Path. so revert that commit.

REFMAIL: 20240818002409.4c918eb4@inari

src/drv_maildir.c

@@ -372,6 +372,8 @@ maildir_list_maildirpp( maildir_store_t *ctx, int flags, const char *inbox )
 	return 0;
 }
 
+static int maildir_list_inbox( maildir_store_t *ctx );
+
 static int
 maildir_list_recurse( maildir_store_t *ctx, int isBox,
                       const char *inbox, uint inboxLen,
@@ -422,6 +424,10 @@ maildir_list_recurse( maildir_store_t *ctx, int isBox,
 		pl += pathLen;
 		if (inbox && equals( path, pl, inbox, inboxLen )) {
 			// Inbox nested into Path.
+			if (maildir_list_inbox( ctx ) < 0) {
+				closedir( dir );
+				return -1;
+			}
 		} else {
 			if (style == SUB_LEGACY) {
 				if (*ent == '.') {