I myself deal with this specific case for a paid application and a trial version with the same code base. I use SVN, but any versioning software that supports branching will work.
I created a branch for the trial version from the torso.
Then I changed the test file AndroidManifest.xml to change the package name, adding .trial to the end. Then I also had to update all the java activity files to refer to the correct R class.
My paid application package is com.hewittsoft.baby
My trial application package is com.hewittsoft.baby.trial
In my actions on the trial branch, I do this
import com.hewittsoft.baby.trial.R;
and calls references to R.id.textField (or something else).
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