title: making a shell 'source' file use relative paths
body: <p>I have the file: myvars</p>
  
  <pre><code>MONO_PREFIX=/opt/mono
  export MONO_PATH=$MONO_PREFIX/lib/mono/2.0
  </code></pre>
  
  <p>I "use" it, by calling:</p>
  
  <pre><code>source myvars
  </code></pre>
  
  <p>I want to change <code>/opt/mono</code> to be relative to the location of the myvars file instead of being absolute. How could I do this?</p>