The mariabackup tool currently reads the [xtrabackup] option group from configuration files. It inherited this behavior from Percona XtraBackup, and it probably makes sense to keep it. However, wouldn't it also make sense for mariabackup to read the [mariabackup] option group? It doesn't currently seem to do so.
e.g. if someone wants to set a user name and password, they can currently do the following:
But maybe it would make sense to also support the following?: