Don't update upload paths twice

This will be done in
20170717150329_enqueue_migrate_system_uploads_to_new_folder.rb
instead.

db/post_migrate/20170317162059_update_upload_paths_to_system.rb

-# See http://doc.gitlab.com/ce/development/migration_style_guide.html
-# for more information on how to write migrations for GitLab.
-
-class UpdateUploadPathsToSystem < ActiveRecord::Migration
-  include Gitlab::Database::MigrationHelpers
-
-  DOWNTIME = false
-  AFFECTED_MODELS = %w(User Project Note Namespace Appearance)
-
-  disable_ddl_transaction!
-
-  def up
-    update_column_in_batches(:uploads, :path, replace_sql(arel_table[:path], base_directory, new_upload_dir)) do |_table, query|
-      query.where(uploads_to_switch_to_new_path)
-    end
-  end
-
-  def down
-    update_column_in_batches(:uploads, :path, replace_sql(arel_table[:path], new_upload_dir, base_directory)) do |_table, query|
-      query.where(uploads_to_switch_to_old_path)
-    end
-  end
-
-  # "SELECT \"uploads\".* FROM \"uploads\" WHERE \"uploads\".\"model_type\" IN ('User', 'Project', 'Note', 'Namespace', 'Appearance') AND (\"uploads\".\"path\" ILIKE 'uploads/%' AND NOT (\"uploads\".\"path\" ILIKE 'uploads/system/%'))"
-  def uploads_to_switch_to_new_path
-    affected_uploads.and(starting_with_base_directory).and(starting_with_new_upload_directory.not)
-  end
-
-  # "SELECT \"uploads\".* FROM \"uploads\" WHERE \"uploads\".\"model_type\" IN ('User', 'Project', 'Note', 'Namespace', 'Appearance') AND (\"uploads\".\"path\" ILIKE 'uploads/%' AND \"uploads\".\"path\" ILIKE 'uploads/system/%')"
-  def uploads_to_switch_to_old_path
-    affected_uploads.and(starting_with_new_upload_directory)
-  end
-
-  def starting_with_base_directory
-    arel_table[:path].matches("#{base_directory}/%")
-  end
-
-  def starting_with_new_upload_directory
-    arel_table[:path].matches("#{new_upload_dir}/%")
-  end
-
-  def affected_uploads
-    arel_table[:model_type].in(AFFECTED_MODELS)
-  end
-
-  def base_directory
-    "uploads"
-  end
-
-  def new_upload_dir
-    File.join(base_directory, "system")
-  end
-
-  def arel_table
-    Arel::Table.new(:uploads)
-  end
-end

spec/migrations/update_upload_paths_to_system_spec.rb

-require "spec_helper"
-require Rails.root.join("db", "post_migrate", "20170317162059_update_upload_paths_to_system.rb")
-
-describe UpdateUploadPathsToSystem do
-  let(:migration) { described_class.new }
-
-  before do
-    allow(migration).to receive(:say)
-  end
-
-  describe "#uploads_to_switch_to_new_path" do
-    it "contains only uploads with the old path for the correct models" do
-      _upload_for_other_type = create(:upload, model: create(:ci_pipeline), path: "uploads/ci_pipeline/avatar.jpg")
-      _upload_with_system_path = create(:upload, model: create(:project), path: "uploads/system/project/avatar.jpg")
-      _upload_with_other_path = create(:upload, model: create(:project), path: "thelongsecretforafileupload/avatar.jpg")
-      old_upload = create(:upload, model: create(:project), path: "uploads/project/avatar.jpg")
-      group_upload = create(:upload, model: create(:group), path: "uploads/group/avatar.jpg")
-
-      expect(Upload.where(migration.uploads_to_switch_to_new_path)).to contain_exactly(old_upload, group_upload)
-    end
-  end
-
-  describe "#uploads_to_switch_to_old_path" do
-    it "contains only uploads with the new path for the correct models" do
-      _upload_for_other_type = create(:upload, model: create(:ci_pipeline), path: "uploads/ci_pipeline/avatar.jpg")
-      upload_with_system_path = create(:upload, model: create(:project), path: "uploads/system/project/avatar.jpg")
-      _upload_with_other_path = create(:upload, model: create(:project), path: "thelongsecretforafileupload/avatar.jpg")
-      _old_upload = create(:upload, model: create(:project), path: "uploads/project/avatar.jpg")
-
-      expect(Upload.where(migration.uploads_to_switch_to_old_path)).to contain_exactly(upload_with_system_path)
-    end
-  end
-
-  describe "#up", truncate: true do
-    it "updates old upload records to the new path" do
-      old_upload = create(:upload, model: create(:project), path: "uploads/project/avatar.jpg")
-
-      migration.up
-
-      expect(old_upload.reload.path).to eq("uploads/system/project/avatar.jpg")
-    end
-  end
-
-  describe "#down", truncate: true do
-    it "updates the new system patsh to the old paths" do
-      new_upload = create(:upload, model: create(:project), path: "uploads/system/project/avatar.jpg")
-
-      migration.down
-
-      expect(new_upload.reload.path).to eq("uploads/project/avatar.jpg")
-    end
-  end
-end