title: Copy if not exist in WiX
body: <p>I have a config file, myapp.exe.config, that I want to install only if it does not already exist. That is, I don't want to overwrite any existing config file. How can this be done in WiX?</p>
  
  <p>(Ultimately I will have to do something more sophisticated with settings, having defaults and overrides and so on. But in the meantime I am just looking for a short-term fix.)</p>