When using embedded server configuration file outside of the directory $EAP_HOME/standalone/configuration error message occurs:

Cannot start embedded server: WFLYEMB0022: Cannot invoke 'start' on embedded process: WFLYCTL0214: Could not get main file: ../../appclient/configuration/appclient.xml. Specified 
files must be relative to the configuration dir:

Especially the second part of the message starting "Specified
files must be relative to the configuration dir" is misleading for the user as the relative path was provided by -c=../../appclient/configuration/appclient.xml. In other words it could be great to mention that configuration dir could be set by the property jboss.server.config.dir during jboss-cli start.