[RFE] Remove downgrade support from migrations

[Anton Arefiev]

Many migrations in OpenStack include data-manipulation to ensure the data conforms to the new schema; often these data-migrations are difficult or impossible to reverse without significant overhead. Performing a downgrade of the schema with such data manipulation can lead to inconsistent or broken state. The possibility of bad-states, relatively minimal testing, and no demand for support renders a downgrade of the schema an unsafe action.

Cross project spec about eliminate db downgrade migration was approved:
https://github.com/openstack/openstack-specs/blob/master/specs/no-downward-sql-migration.rst

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/258991

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/258991
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=49e0475b03992adbec4a8271a25e0ab09bbc89fb
Submitter: Jenkins
Branch: master

commit 49e0475b03992adbec4a8271a25e0ab09bbc89fb
Author: Anton Arefiev <email address hidden>
Date: Thu Dec 17 14:51:29 2015 +0200

    Remove downgrade support from migrations

    According to cross project spec I622f89fe63327d44f9b229d3bd9e76e15acbaa7a
    downgrade migrations should be removed.
    Also related tests was removed.

    Closes-Bug: #1527248
    Change-Id: I048bd73243d03b03080255c7cfeb53043f10acc5

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/ironic 5.0.0 release.