How to set system properties for runMain on command line?

This works:

sbt '; set javaOptions += "-Dconfig.resource=../application.conf" ; runMain akka.Main com.my.main.Actor'

If this isn’t a “friendly” enough syntax, wrap it in a little shell script.

(Note this assumes you have fork set to true for running. If you don’t, see akauppi’s comment.)