on_conflict_behavior

# File railties/lib/rails/generators/actions/create_migration.rb, line 48
          def on_conflict_behavior # :doc:
            options = base.options.merge(config)
            if identical?
              say_status :identical, :blue, relative_existing_migration
            elsif options[:force]
              say_status :remove, :green, relative_existing_migration
              say_status :create, :green
              unless pretend?
                ::FileUtils.rm_rf(existing_migration)
                yield
              end
            elsif options[:skip]
              say_status :skip, :yellow
            else
              say_status :conflict, :red
              raise Error, "Another migration is already named #{migration_file_name}: "                  "#{existing_migration}. Use --force to replace this migration "                  "or --skip to ignore conflicted file."
            end
          end