Migration to change data type of existing column from string to text

I have been poking around the rails guides section on migrations
(Ruby on Rails Guides: Migrations)
and trying to make sure I have the proper syntax to change a column
type for an existing field from string to text (without losing data
already entered). What is the proper syntax for this in a migration?

Let’s say for this example, the table is named “posts” and the column
is named “apply_info”

Well googled a bit more as I am impatient. Credit for this answer goes
to
http://www.cowboycoded.com/2009/10/07/change-a-column-data-type-with-rails-migration/

Thanks cowboy.