I asked that question on the mailing list and the short answer is, basically the same way you do with Distillery. Release tasks in Distillery are just custom commands, and what the guide for migrations does is a custom command that evals a function. You can do that in 1.9 releases as well. So it’s the exact same thing, except instead of
app/bin/hello migrate
you run
app/bin/hello eval "Hello.ReleaseTasks.migrate"
https://groups.google.com/forum/#!topic/elixir-lang-core/OkJ9C4U-C-k
