Merge pull request #2529 from lampepfl/DarkDimius-patch-2

Report that we are not scalac but dotc in help output

Author: liufengyun

compiler/src/dotty/tools/dotc/config/CompilerCommand.scala

@@ -11,7 +11,7 @@ import Properties._
 object CompilerCommand extends DotClass {
 
   /** The name of the command */
-  def cmdName = "scalac"
+  def cmdName = "dotc"
 
   private def explainAdvanced = """
     |-- Notes on option parsing --