const connectionSettings = {
  client: 'mysql2',
  connection: {
    host: '127.0.0.1',
    user: 'mysql',
    password: 'mysql',
    database: 'db'
  }
};

const migrations = {
  directory: path.resolve(__dirname, 'back/database/migrations'),
  tableName: 'knex_migrations',
};

const development = Object.assign(connectionSettings, {
  migrations,
  seeds: {
    directory: path.resolve(__dirname, 'back/database/seeds/development')
  }
});

console.log(development.seeds.directory); // ?

const production = Object.assign(connectionSettings, {
  migrations,
  seeds: {
    directory: path.resolve(__dirname, 'back/database/seeds/production')
  }
});

console.log(development.seeds.directory); // ?