* Prepend !shell to the commands to run when shell is the last command specified by the user.

* def.scala.version no longer required to be in build.properties

src/main/scala/sbt/Main.scala

@@ -87,11 +87,15 @@ class xMain extends xsbti.AppMain
 			}
 		}
 	}
+	/** If no arguments are provided, drop to interactive prompt.
+	* If the user wants to run commands before dropping to the interactive prompt,
+	*   make dropping to the interactive prompt the action to perform on failure */
 	private def initialize(args: List[String]): List[String] =
 		args.lastOption match
 		{
 			case None => InteractiveCommand :: Nil
-			case Some(InteractiveCommand | ExitCommand | QuitCommand) => args
+			case Some(InteractiveCommand) => (FailureHandlerPrefix + InteractiveCommand) :: args
+			case Some(ExitCommand | QuitCommand) => args
 			case _ => args ::: ExitCommand :: Nil
 		}
 	private def startProject(project: Project, configuration: xsbti.AppConfiguration, remainingArguments: List[String], startTime: Long): xsbti.MainResult =

src/main/scala/sbt/Project.scala

@@ -213,9 +213,8 @@ trait Project extends TaskManager with Dag[Project] with BasicEnvironment
 	final val projectOrganization = propertyOptional[String](normalizedName, true)
 	/** The property that defines the version of Scala to use with the project definition.  This can be different
 	* from the version of Scala used to build the project (current version used is buildScalaVersion, available are in buildScalaVersions).
-	* This property is only read by `sbt` on startup and reload. It is the definitive source for the version of Scala
-	* that sbt and the project definition are using.*/
-	final val defScalaVersion = property[String]
+	* This property is only read by `sbt` on startup and reload.*/
+	final val defScalaVersion = propertyOptional[String](info.definitionScalaVersion)
 	final val sbtVersion = property[String]
 	final val projectInitialize = propertyOptional[Boolean](false)
 	final val projectScratch = propertyOptional[Boolean](false, true)