alphagov/publisher — pull request #319 by rboulton (2014-11-28 12:15:29+00:00)
Title: topic_changes:prepare takes output file parameter

We want to be able to run the topic_changes:prepare task from rake.
To do this effectively, we need to be able to determine where the output
file is going to be generated.

This PR adds that as a required argument. For safety, it also checks
that the output file doesn't exist already, to avoid overwriting files
by mistake.