Migrations rollback in production environment

Please provide a patch (https://rails.lighthouseapp.com/projects/8994/sending-patches) with a fix and/or a failing test.

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[state:open]

Yes, I think this is important feature for rails.

It is connected with production releases and complex migrations when the data should be changed significantly.
All this process use to fail sometimes.

In this case if we could rollback the database to the state before migration - we would never have problems with failed deployments.

Will provide the failing test.