delete_old_migrations.rb

version = 3.months.ago.utc.strftime("%Y%m%d%H%M%S")

puts "Deleting migrations before version #{version.inspect}"

migrations =
  ActiveRecord::MigrationContext.new(['db/migrate'])
    .migrations
    .take_while { |migration| migration.version < version }

File.delete(*migrations.map(&:filename))

delete_old_versions.rb

# frozen_string_literal: true

class DeleteOldSchemaMigrationVersions < ActiveRecord::Migration[5.2]
  def up
    ActiveRecord::SchemaMigration.where("version < ?", <version>).delete_all
  end

  def down; end
end