title: How to specify Octopus built-in variable names in an XML configuration file?
body: <p>We are testing Octopus Deploy, so we made a sample web.config file that we installed and transform in different environments. web.config transformation and use of custom variable work fine, but I can't get build-in Octopus variables to be substituted. Here's an example of of XML section in web.config:</p>
  
  <pre><code>  &lt;appSettings&gt;
      &lt;add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" /&gt;
      &lt;add key="environmentTransform" value="" /&gt;
      &lt;add key="EnvironmentVariable1" value="$OctopusEnvironmentName" /&gt;
      &lt;add key="EnvironmentVariable2" value="$(OctopusEnvironmentName)" /&gt;
      &lt;add key="EnvironmentVariable3" value="$(Octopus.Environment.Name)" /&gt;
      &lt;add key="EnvironmentVariable4" value="$Octopus.Environment.Name)" /&gt;
      &lt;add key="EnvironmentVariable5" value="$OctopusParameters[&amp;quot;Octopus.Environment.Name&amp;quot;]" /&gt;
      &lt;add key="MachineVariable1" value="$Octopus.Machine.Name" /&gt;
      &lt;add key="MachineVariable2" value="#(Octopus.Machine.Name)" /&gt;
      &lt;add key="MachineVariable3" value="#OctopusMachineName" /&gt;
      &lt;add key="CustomVariable" value="CustomVariable" /&gt;
    &lt;/appSettings&gt;
  </code></pre>
  
  <p>And here's web.Dev.config, named after the environment:</p>
  
  <pre><code>  &lt;appSettings&gt;
      &lt;add key="environmentTransform" value="Dev" xdt:Transform="SetAttributes" xdt:Locator="Match(key)"/&gt;
    &lt;/appSettings&gt;
  </code></pre>
  
  <p>And here's the result:</p>
  
  <pre><code>  &lt;appSettings&gt;
      &lt;add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" /&gt;
      &lt;add key="environmentTransform" value="Dev" /&gt;
      &lt;add key="EnvironmentVariable1" value="$OctopusEnvironmentName" /&gt;
      &lt;add key="EnvironmentVariable2" value="$(OctopusEnvironmentName)" /&gt;
      &lt;add key="EnvironmentVariable3" value="$(Octopus.Environment.Name)" /&gt;
      &lt;add key="EnvironmentVariable4" value="$Octopus.Environment.Name)" /&gt;
      &lt;add key="EnvironmentVariable5" value="$OctopusParameters[&amp;quot;Octopus.Environment.Name&amp;quot;]" /&gt;
      &lt;add key="MachineVariable1" value="$Octopus.Machine.Name" /&gt;
      &lt;add key="MachineVariable2" value="#(Octopus.Machine.Name)" /&gt;
      &lt;add key="MachineVariable3" value="#OctopusMachineName" /&gt;
      &lt;add key="CustomVariable" value="Value for maeaint01" /&gt;
    &lt;/appSettings&gt;
  </code></pre>
  
  <p>As you can see, Octopus variables are not replaced. Any idea why?</p>