title: In SBT 0.13, does scalaVersion still control the version of scala used for compile, run and test?
body: <p>When upgrading our build from 12.4 to 13.1 I observed that although the build specified <code>scalaVersion := "2.10.2"</code>, the resulting archive (created via the sbt-pack plugin) contained scala-library-2.10.3.jar.  A quick check confirmed that the 12.4 build was including scala-library-2.10.2.jar.</p>
  
  <p>It appears that sbt 0.13 included a change to treat the scala libraries as normal dependencies, with the consequence that if a project dependency was built with a later 2.10.x version of scala then that transitive dependency will "win" the ivy dependency resolution conflict resolution, and the compile, test and run classpaths will contain the later version of scala libraries.</p>
  
  <p><strong>Is this the desired behavior, or a bug in sbt 0.13?</strong></p>
  
  <p>If the desired behavior, then does that mean I have to use the mechanisms to "force/override" the conflict resolution to use my desired version of the scala libraries?  (If so, the scalaVersion configuration setting seems a bit pointless....)</p>
  
  <p>Here is an extremely minimal test case to illustrate the behavior:</p>
  
  <pre><code>test-proj/
    build.sbt
    project/
      build.properties
  </code></pre>
  
  <p>build.sbt:</p>
  
  <pre><code>scalaVersion := "2.10.2"
  //scalaVersion := "2.10.3"
  
  libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.3.0"
  //libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.2.4"
  </code></pre>
  
  <p>build.properties:</p>
  
  <pre><code>sbt.version=0.13.1
  </code></pre>
  
  <p>Akka 2.2.4 was built against scala 2.10.2, so firing up sbt and running "update", "show update", "show compile:dependencyClasspath", "show test:dependencyClasspath" and "show runtime:dependencyClasspath" all show scala-library 2.10.2 on the classpath.</p>
  
  <p>Switching to Akka 2.3.0, which was built against scala 2.10.3, results in scala-library 2.10.3 appearing on all the classpaths, and "show update" clearly shows 2.10.2 being evicted by Ivy's conflict resolution.</p>
  
  <p>Interestingly (and inconsistently), entering the REPL in both cases (via the sbt console command) results in scala 2.10.2 being utilized.</p>
  
  <p>According to the <a href="http://www.scala-sbt.org/release/docs/Howto/scala.html" rel="noreferrer">docs</a>, in sbt 0.13 </p>
  
  <blockquote>
    <p>The scalaVersion configures the version of Scala used for compilation. By default, sbt also adds a dependency on the Scala library with this version.</p>
  </blockquote>
  
  <p>Based on that, I would expect the compilation classpath above to include 2.10.2 in both circumstances.</p>
  
  <p>However, <a href="http://www.scala-sbt.org/release/docs/Community/ChangeSummary_0.13.0.html" rel="noreferrer">the release notes for 0.13</a> say</p>
  
  <blockquote>
    <p>Scala dependencies (like scala-library and scala-compiler) are now resolved via the normal update task</p>
  </blockquote>
  
  <p>which does at least explain the observed behavior.</p>