title: Why does sbt keep telling me to add -deprecation to scalacOptions when it's already?
body: <p>Here below is my multi-project structure:</p>
  
  <pre><code>myApp
    + build.sbt
    + sub-prj-1
        + build.sbt
    + sub-prj-2
        + build.sbt
    + project
        + Build.scala
  </code></pre>
  
  <p>I use to define common settings in <code>project/Build.scala</code> like this:</p>
  
  <pre><code>import sbt._
  import Keys._
  
  object ApplicationBuild extends Build {
  
    val defaultScalacOptions = Seq(
      "-unchecked", "-deprecation", "-feature", "-language:reflectiveCalls", "-language:implicitConversions",
      "-language:postfixOps", "-language:dynamics", "-language:higherKinds", "-language:existentials",
      "-language:experimental.macros", "-encoding", "UTF-8", "-Xmax-classfile-name", "140")
  
    val defaultResolvers = Seq(
      "Typesafe releases repository" at "http://repo.typesafe.com/typesafe/releases/"
    )
  
    val defaultSettings = Defaults.defaultSettings ++ Seq(
      scalaVersion := "2.10.4",
      scalacOptions ++= defaultScalacOptions,
      resolvers ++= defaultResolvers
    )
  }
  </code></pre>
  
  <p>... and then I reference these common settings in each <code>build.sbt</code> file:</p>
  
  <pre><code>name := "myapp"
  
  organization := "Test, Inc."
  
  version := "1.0"
  
  ApplicationBuild.defaultSettings // it looks like common settings defined in
                                   // project/Build.scala are not read...
  
  scalacOptions += "-feature"      // already defined in ApplicationBuild.defaultSettings...
                                   // but if I don't define it here, it doesn't work
  
  lazy val `sub-prj-1` = project.in(file("sub-prj-1"))
  
  lazy val `sub-prj-2` = project.in(file("sub-prj-2"))
  
  lazy val brix = project.in(file(".")).settings(
    publishArtifact := false
  ).aggregate(
    `sub-prj-1`,
    `sub-prj-2`
  )
  </code></pre>
  
  <p>For example, <code>scalacOptions += "-feature"</code> is already defined in <code>Build.scala</code>... but if I don't define it in <code>build.sbt</code> I always get the following warning:</p>
  
  <pre><code>[warn] there were 1 deprecation warning(s); re-run with -deprecation for details
  [warn] one warning found
  </code></pre>
  
  <p>Any idea? Am I missing something? This problem first appeared after I installed sbt 0.13.5.</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>Here's the content of <code>scalacOptions</code>:</p>
  
  <pre><code>[info] sub-prj-1/*:scalacOptions
  [info]  List(-unchecked, -deprecation, -feature, -language:reflectiveCalls, -language:implicitConversions, -language:postfixOps, -language:dynamics, -language:higherKinds, -language:existentials, -language:experimental.macros, -encoding, UTF-8, -Xmax-classfile-name, 140)
  [info] sub-prj-2/*:scalacOptions
  [info]  List(-unchecked, -deprecation, -feature, -language:reflectiveCalls, -language:implicitConversions, -language:postfixOps, -language:dynamics, -language:higherKinds, -language:existentials, -language:experimental.macros, -encoding, UTF-8, -Xmax-classfile-name, 140)
  [info] myapp/*:scalacOptions
  [info]  List(-unchecked, -deprecation, -feature, -language:reflectiveCalls, -language:implicitConversions, -language:postfixOps, -language:dynamics, -language:higherKinds, -language:existentials, -language:experimental.macros, -encoding, UTF-8, -Xmax-classfile-name, 140)
  </code></pre>