* [feature] [operations] Added Operations.implementation_for.replace parameter to
Operations.implementation_for(), allowing replacement of existing
operation implementations. This allows for existing operations such as
CreateTableOp to be extended directly.
* [bug] [mssql] Fixed issue in SQL Server dialect where the DROP that's automatically
emitted for existing default constraints during an ALTER COLUMN needs to
take place before not just the modification of the column's default, but
also before the column's type is changed.
OBS-URL: https://build.opensuse.org/package/show/devel:languages:python/python-alembic?expand=0&rev=178
