Update migration constant

Update the data migration current release to 'yoga'.  Include a
semver pseudo-header in this commit message so that pbr will
increment the major version number, otherwise
glance.tests.unit.gate.test_data_migration_version will break.

Also add a reminder about this to the release cycle tasks list.

Change-Id: Ibdbeb752d29afeb48628587442577ab139be9ac9
Sem-Ver: api-break

doc/source/contributor/releasecycle.rst

@@ -24,6 +24,18 @@ Between Summit and Milestone-1
 #. Add any Glance-specific schedule information to the release calendar
    (https://review.opendev.org/#/c/505425/)
 
+#. Update the ``CURRENT_RELEASE`` constant in ``glance/db/migration.py``.
+   Include a ``Sem-Ver`` pseudo-header in the commit message so that
+   PBR will increment the glance version number to match the release
+   name.
+
+   * The value of the ``Sem-Ver`` pseudo-header must be ``api-break``
+     (which is a little disconcerting) because we need to increment the
+     major digit in the **Glance** version number (we aren't signalling
+     anything about the **Images** API), and that's the constant
+     that pbr recognizes for this purpose.
+   * Example patch: https://review.opendev.org/c/openstack/glance/+/827919
+
 #. Focus on spec reviews to get them approved and updated early in
    the cycle to allow enough time for implementation.
 

glance/db/migration.py

@@ -29,5 +29,5 @@ db_options.set_defaults(cfg.CONF)
 # Migration-related constants
 EXPAND_BRANCH = 'expand'
 CONTRACT_BRANCH = 'contract'
-CURRENT_RELEASE = 'xena'
+CURRENT_RELEASE = 'yoga'
 ALEMBIC_INIT_VERSION = 'liberty'