Big ol' start of the SQL migrations system.

Things definitely don't work yet, but should be heading in the right direction.

mediagoblin/db/sql/migrations.py

@@ -0,0 +1,17 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+MIGRATIONS = []

mediagoblin/db/sql/models.py

@@ -216,6 +216,27 @@ class MediaComment(Base):
     get_author = relationship(User)
 
 
+MODELS = [
+    User, MediaEntry, Tag, MediaTag, MediaComment]
+
+
+######################################################
+# Special, migrations-tracking table
+#
+# Not listed in MODELS because this is special and not
+# really migrated, but used for migrations (for now)
+######################################################
+
+class MigrationData(Base):
+    __tablename__ = "migrations"
+
+    id = Column(Integer, primary_key=True)
+    name = Column(Unicode, nullable=False, unique=True)
+    version = Column(Integer, nullable=False, default=0)
+
+######################################################
+
+
 def show_table_init():
     from sqlalchemy import create_engine
     engine = create_engine('sqlite:///:memory:', echo=True)

mediagoblin/db/sql/util.py

@@ -0,0 +1,59 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+class MigrationManager(object):
+    pass
+
+
+class RegisterMigration(object):
+    """
+    Tool for registering migrations
+
+    Call like:
+
+    @RegisterMigration(33)
+    def update_dwarves(database):
+        [...]
+
+    This will register your migration with the default migration
+    registry.  Alternately, to specify a very specific
+    migration_registry, you can pass in that as the second argument.
+
+    Note, the number of your migration should NEVER be 0 or less than
+    0.  0 is the default "no migrations" state!
+    """
+    def __init__(self, migration_number, migration_registry):
+        assert migration_number > 0, "Migration number must be > 0!"
+        assert migration_number not in migration_registry, \
+            "Duplicate migration numbers detected!  That's not allowed!"
+
+        self.migration_number = migration_number
+        self.migration_registry = migration_registry
+
+    def __call__(self, migration):
+        self.migration_registry[self.migration_number] = migration
+        return migration
+
+
+def assure_migrations_table_setup(db):
+    """
+    Make sure the migrations table is set up in the database.
+    """
+    from mediagoblin.db.sql.models import MigrationData
+
+    if not MigrationData.__table__.exists(db):
+        MigrationData.metadata.create_all(
+            db, tables=[MigrationData.__table__])