Comment 6 for bug 414997

I'll make this argument one last time, then I promise to let it be.
I believe that the correct fix for this bug is the attached patch below.

What it does, is simply put comment headers in the files that are modified by ec2-set-defaults to inform the user that they should be modifying the template file if they want their changes to be carried through a re-bundle.

The reasons I think this is the best approach are:
a.) "by default" allows the user to take advantage of the run-time decisions that ec2-set-defaults is making. The example that I think of that doesn't fit "if the user changed this, then leave it be", is that if the user added a /etc/apt/sources.list entry, rebundles their' US region image with that change, and them publishes to EU region, they'll not use the EU region mirror.
b.) documents to the user the behavior in a obvious place (the config file they're changing)
c.) allows the user to ignore changes ec2-set-defaults would make (by removing the variables in the template)