title: Is SBT build considered reliable for a regular deployment without clean?
body: <p>When deploying a Scala application, we use SBT on Jenkins. Currently our build action is specified as <code>clean assembly</code> (using <a href="https://github.com/sbt/sbt-assembly" rel="nofollow">Assembly plugin</a> to produce fat JARs). Our build currently takes between 2-3 minutes, which is sensible, but as the project will become larger and deployments for frequent, it might become a bottleneck.</p>
  
  <p>I remember when doing C++ deployment with Visual Studio, clean (Rebuild All) was necessary, otherwise builds were sometimes (say 0.1%) broken (most likely because build missed some changed dependency in headers).</p>
  
  <p>Is this a concern with SBT? Is <code>clean</code> considered a necessary practice to get reliable builds?</p>