-Ylog:X now only log phase X, use -Ylog:X+ to also log phase X+1

[smarter]

This supersedes #273.
Review by @odersky .

[odersky]

I believe the logic can be simplified and made clearer as follows:

case _ => 
    names exists { n =>
       n == "all" || {
          val strippedName = name.stripSuffix("+")
          val indicatedPhase = if (name == strippedName) phase else phase.prev
          indicatedPhase.phaseName.startsWith(strippedName)
      }
   }  

[smarter]

No, that doesn't work, if we have a "+" we want to match on both phase and phase.prev, we could use a list but that seems overkill, what do you think of:

case _ => 
    names exists { n =>
       n == "all" || {
          val strippedName = name.stripSuffix("+")
          val logNextPhase = name ne strippedName
          phase.phaseName.startsWith(strippedName) ||
            (logNextPhase && phase.prev.phaseName.startsWith(strippedName))
      }
   }

[odersky]

Ah I thought of a different spec. But yours makes more sense, I think. The change looks good.

[odersky]

Otherwise LGTM

[smarter]

Should be good to be merged now.