FIX: Cleanup migrations with timestamps in the future

A future-dated migration was accidently introduced by me in 45c399f0. This was removed in b9762afc, but other migrations had already been generated based on its incorrect date. This commit removes the offending data in the schema_migrations table, and corrects the version in the published_pages migration.

This commit also adds a check to db:migrate which raises an error when invalid migration timestamps are used.

db/migrate/20200617144300_add_public_field_to_published_pages.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class AddPublicFieldToPublishedPages < ActiveRecord::Migration[6.0]
+  def up
+    # Delete the record of https://github.com/discourse/discourse/commit/b9762afc106ee9b18d1ac33ca3cac281083e428e
+    execute <<~SQL
+      DELETE FROM schema_migrations WHERE version='20201006172700'
+    SQL
+
+    # Delete the reference to the incorrectly versioned version of this migration
+    execute <<~SQL
+      DELETE FROM schema_migrations WHERE version='20201006172701'
+    SQL
+
+    # Using IF NOT EXISTS because the version number of this migration was changed
+    # Therefore some sites may have already added the column
+    execute <<~SQL
+      ALTER TABLE "published_pages" ADD COLUMN IF NOT EXISTS "public" boolean DEFAULT FALSE NOT NULL
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

db/migrate/20201006172701_add_public_field_to_published_pages.rb

@@ -1,7 +0,0 @@
-# frozen_string_literal: true
-
-class AddPublicFieldToPublishedPages < ActiveRecord::Migration[6.0]
-  def change
-    add_column :published_pages, :public, :boolean, null: false, default: false
-  end
-end

lib/tasks/db.rake

@@ -187,6 +187,12 @@ end
 
 # we need to run seed_fu every time we run rake db:migrate
 task 'db:migrate' => ['load_config', 'environment', 'set_locale'] do |_, args|
+  migrations = ActiveRecord::Base.connection.migration_context.migrations
+  now_timestamp = Time.now.utc.strftime('%Y%m%d%H%M%S').to_i
+  epoch_timestamp = Time.at(0).utc.strftime('%Y%m%d%H%M%S').to_i
+
+  raise "Migration #{migrations.last.version} is timestamped in the future" if migrations.last.version > now_timestamp
+  raise "Migration #{migrations.first.version} is timestamped before the epoch" if migrations.first.version < epoch_timestamp
 
   ActiveRecord::Tasks::DatabaseTasks.migrate