title: How to disable package and publish tasks for root aggregate module in multi-module build?
body: <p>I have a multiproject SBT project, which looks like the example on SBT doc:</p>
  
  <pre><code>import sbt._
  import Keys._
  
  object HelloBuild extends Build {
    lazy val root = Project(id = "hello",
                          base = file(".")) aggregate(foo, bar)
  
    lazy val foo = Project(id = "hello-foo",
                         base = file("foo"))
  
    lazy val bar = Project(id = "hello-bar",
                         base = file("bar"))
  }
  </code></pre>
  
  <p>Because <code>root</code> is just a virtual project to aggregate both subprojects, I would like to avoid package generation (and artifact publication), but still generate package (and publish) for both subprojects.</p>
  
  <p>Is there an easy way to achieve it ?</p>