Add rake task to drop a project's PostReceive jobs

lib/tasks/gitlab/sidekiq.rake

+namespace :gitlab do
+  namespace :sidekiq do
+    QUEUE = 'queue:post_receive'
+
+    desc 'Drop all Sidekiq PostReceive jobs for a given project'
+    task :drop_post_receive , [:project] => :environment do |t, args|
+      unless args.project.present?
+        abort "Please specify the project you want to drop PostReceive jobs for:\n  rake gitlab:sidekiq:drop_post_receive[group/project]"
+      end
+      project_path = Project.find_with_namespace(args.project).repository.path_to_repo
+
+      Sidekiq.redis do |redis|
+        unless redis.exists(QUEUE)
+          abort "Queue #{QUEUE} is empty"
+        end
+
+        temp_queue = "#{QUEUE}_#{Time.now.to_i}"
+        redis.rename(QUEUE, temp_queue)
+
+        # At this point, then post_receive queue is empty. It may be receiving
+        # new jobs already. We will repopulate it with the old jobs, skipping the
+        # ones we want to drop.
+        dropped = 0
+        while (job = redis.lpop(temp_queue)) do
+          if repo_path(job) == project_path
+            dropped += 1
+          else
+            redis.rpush(QUEUE, job)
+          end
+        end
+        # The temp_queue will delete itself after we have popped all elements
+        # from it
+
+        puts "Dropped #{dropped} jobs containing #{project_path} from #{QUEUE}"
+      end
+    end
+
+    def repo_path(job)
+      job_args = JSON.parse(job)['args']
+      if job_args
+        job_args.first
+      else
+        nil
+      end
+    end
+  end
+end