make handling of Inbox-in-Path nesting less obfuscated

when we run into Inbox while listing Path, check whether Inbox is being
listed anyway, and just skip it if so, instead of listing it right away
and resetting LIST_INBOX (and thus having a calling order dependency).

src/drv_maildir.c

@@ -228,10 +228,10 @@ maildir_invoke_bad_callback( store_t *ctx )
 	ctx->bad_callback( ctx->bad_callback_aux );
 }
 
-static int maildir_list_inbox( store_t *gctx, int *flags );
+static int maildir_list_inbox( store_t *gctx, int flags );
 
 static int
-maildir_list_recurse( store_t *gctx, int isBox, int *flags, const char *inbox, int inboxLen,
+maildir_list_recurse( store_t *gctx, int isBox, int flags, const char *inbox, int inboxLen,
                       char *path, int pathLen, char *name, int nameLen )
 {
 	DIR *dir;
@@ -258,7 +258,8 @@ maildir_list_recurse( store_t *gctx, int isBox, int *flags, const char *inbox, i
 		const char *ent = de->d_name;
 		pl = pathLen + nfsnprintf( path + pathLen, _POSIX_PATH_MAX - pathLen, "%s", ent );
 		if (inbox && equals( path, pl, inbox, inboxLen )) {
-			if (maildir_list_inbox( gctx, flags ) < 0) {
+			/* Inbox nested into Path. List now if it won't be listed separately anyway. */
+			if (!(flags & LIST_INBOX) && maildir_list_inbox( gctx, flags ) < 0) {
 				closedir( dir );
 				return -1;
 			}
@@ -290,11 +291,10 @@ maildir_list_recurse( store_t *gctx, int isBox, int *flags, const char *inbox, i
 }
 
 static int
-maildir_list_inbox( store_t *gctx, int *flags )
+maildir_list_inbox( store_t *gctx, int flags )
 {
 	char path[_POSIX_PATH_MAX], name[_POSIX_PATH_MAX];
 
-	*flags &= ~LIST_INBOX;
 	return maildir_list_recurse(
 	        gctx, 2, flags, 0, 0,
 	        path, nfsnprintf( path, _POSIX_PATH_MAX, "%s", ((maildir_store_conf_t *)gctx->conf)->inbox ),
@@ -302,7 +302,7 @@ maildir_list_inbox( store_t *gctx, int *flags )
 }
 
 static int
-maildir_list_path( store_t *gctx, int *flags )
+maildir_list_path( store_t *gctx, int flags )
 {
 	const char *inbox = ((maildir_store_conf_t *)gctx->conf)->inbox;
 	char path[_POSIX_PATH_MAX], name[_POSIX_PATH_MAX];
@@ -319,8 +319,8 @@ static void
 maildir_list_store( store_t *gctx, int flags,
                     void (*cb)( int sts, void *aux ), void *aux )
 {
-	if (((flags & LIST_PATH) && maildir_list_path( gctx, &flags ) < 0) ||
-	    ((flags & LIST_INBOX) && maildir_list_inbox( gctx, &flags ) < 0)) {
+	if (((flags & LIST_PATH) && maildir_list_path( gctx, flags ) < 0) ||
+	    ((flags & LIST_INBOX) && maildir_list_inbox( gctx, flags ) < 0)) {
 		maildir_invoke_bad_callback( gctx );
 		cb( DRV_CANCELED, aux );
 	} else {