how to set main class in SBT 0.13 project

Could you guys please explain to me how to set main class in SBT project ? I'm trying to use version 0.13. My directory structure is very simple (unlike SBT's documentation). In the root folder I have `build.sbt` with following content ``` name := "sbt_test" version := "1.0" scalaVersion := "2.10.1-local" autoScalaLibrary := false scalaHome := Some(file("/Program Files (x86)/scala/")) mainClass := Some("Hi") libraryDependencies ++= Seq( "org.scalatest" % "scalatest_2.10" % "2.0.M5b" % "test" ) EclipseKeys.withSource := true ``` And I have subfolder `project` with single file `Hi.scala` which contains following code ``` object Hi { def main(args: Array[String]) = println("Hi!") } ``` I'm able to compile it by calling `sbt compile` but `sbt run` returns ``` The system cannot find the file C:\work\externals\sbt\bin\sbtconfig.txt. [info] Loading project definition from C:\work\test_projects\sbt_test\project [info] Set current project to sbt_test (in build file:/C:/work/test_projects/sbt_test/) java.lang.RuntimeException: No main class detected. at scala.sys.package$.error(package.scala:27) [trace] Stack trace suppressed: run last compile:run for the full output. [error] (compile:run) No main class detected. [error] Total time: 0 s, completed Apr 8, 2013 6:14:41 PM ```