regression: command line MiMa performs no checks unless --direction ... is provided

[retronym]

Regressed in 2844ffa#diff-3383cbf2c9d69641a9962eba1953e3a0R118 (both forwards and backwards checks use direction.getOrElse(Nil) (that's odd in itself, why Nil rather than ""?)

Currently, the SBT build for Scala calls Main directly rather than using the SBT plugin. As such, we've been flying blind (and been blind to our blindness).

[SethTisue]

great catch. one hopes pretty much everybody (but us) has been using the sbt plugin :-\