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Migrations are versioned in Rails 5 | BigBinary Blog
Rails 5 migration classes look like this now:
class CreateUsers < ActiveRecord::Migration[5.0]
Mind the [5.0] at the end.
They do this to evolve the ActiveRecord::Migration API without breaking your historical migrations in db/migrate.
Posted by Henning Koch to makandra dev (2016-09-22 09:33)