[feature] Support for variables within variables?

[Robert Munteanu]

Hi,

I noticed that variables are declared to be supported as part of
configurations and framework properties. In addition to that, I think
it would be very useful to replace them in variable values as well. It
would go well with providing reasonable defaults which can then be
overriden from the command line.

As an example, the following feature file:

{
  "variables": {
    "persistence.dir": "${sling.home}/persistence"
  },
  "configurations": {
    "com.foo.Persister": {
      "data": "${persistence.dir}"
    }
  }
}

will by default store data under launcher/persistence. However, I will
be able to redirect it anywhere with 

  -V persistence.dir=/data

Right now this isn't possible. Is this something that could be done
with the feature model?

Thanks,
Robert