title: How to specify a build folder in Travis?
body: <p>I have a github repository <code>user/repo</code> but the real project is in a subfolder <code>user/repo/project/build.sbt</code><br>
  What should I write in the <code>.travis.yml</code> to make Travis ignore the top folder and work only in the project folder?</p>
  
  <p>Inspired by <a href="https://stackoverflow.com/questions/14006810/how-do-i-get-travis-build-working-directory-in-travis-yml">this</a> I tried the following which didn't work:</p>
  
  <pre><code>env:
    global:
      - REPO="user/repo"
      - CI_HOME=`pwd`/$REPO
  script: sh -c 'cd $CI_HOME/project' &amp;&amp; sbt ++$TRAVIS_SCALA_VERSION package
  </code></pre>
  
  <p>Error log:</p>
  
  <pre><code>$ sh -c 'cd $CI_HOME/project' &amp;&amp; sbt ++$TRAVIS_SCALA_VERSION package
  Detected sbt version 0.12.2-RC1
  /home/travis/build/user/repo doesn't appear to be an sbt project.
  </code></pre>
  
  <p>Ideally there should be a way to specify the build folder but let Travis handle the build command.</p>