"""Backfill NULL merge_strategy rows to 'state_overlay'.

Every proposal is a merge operation and must have a strategy. NULL means the
row was created before the default was enforced. This migration backfills all
existing NULL values to the canonical default.

Revision ID: 0050
Revises: 0049
"""
from __future__ import annotations

import sqlalchemy as sa
from alembic import op

revision: str = "0050"
down_revision: str = "0049"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.execute(
        sa.text(
            "UPDATE musehub_proposals SET merge_strategy = 'state_overlay' "
            "WHERE merge_strategy IS NULL"
        )
    )


def downgrade() -> None:
    pass  # NULL backfills are not reversible