title: what goes into a minimal stack.yaml file?
body: <p>I have projects compiling with <code>cabal build</code> (but using <code>hpack</code> for the convenience). For some reason, I would like to compile them with <code>stack build</code>. What goes into a minimal <code>stack.yaml</code> file?</p>
  <p>The stack documentation gives details what goes into such a file, but does not show a minimal (or any, as much as I can see) example. I fear to use <code>stack init</code> on an existing project for unintended consequences.</p>
  <p>What is a small example from which to go?</p>