Comment 7 for bug 1490990

I guess another project that is involved here is oslo.config since it does not allow to get all config-dirs passed to an executable, instead rewriting the single value on each --config-dir argument occurrence:

https://github.com/openstack/oslo.config/blob/master/oslo_config/cfg.py#L1276

I believe oslo.config should provide a way to get the ordered list of all config dirs and files.