Add `rake gitlab:migrate:shell_hooks`

db/migrate/20140903115954_migrate_to_new_shell.rb.skip

+class MigrateToNewShell < ActiveRecord::Migration
+  def change
+    # The migration was performed by the rake task
+  end
+end

lib/tasks/gitlab/migrate/shell_hooks.rake

+namespace :gitlab do
+  namespace :migrate do
+    task shell_hooks: :environment do
+      migration_file = Rails.root.join('db/migrate/20140903115954_migrate_to_new_shell.rb')
+      migration_source_file = "#{migration_file}.skip"
+
+      unless File.exists?(migration_file)
+        begin
+          FileUtils.cp(migration_source_file, migration_file)
+        rescue => ex
+          warn "Please make sure #{migration_file} exists."
+          warn "\n  sudo cp #{migration_source_file} #{migration_file}\n\n"
+          raise ex
+        end
+      end
+
+      gitlab_shell_path = Gitlab.config.gitlab_shell.path
+      unless system("#{gitlab_shell_path}/bin/create-hooks")
+        abort 'Failed to rewrite gitlab-shell hooks in repositories'
+      end
+
+      hooks_migration_id = '20140903115954'
+      unless system(*%W(rake db:migrate:up VERSION=#{hooks_migration_id}))
+        abort "Failed to run migration #{hooks_migration_id}"
+      end
+
+      puts 'Repositories updated with new hooks'
+      begin
+        FileUtils.rm(migration_file)
+      rescue
+        warn "Please remove #{migration_file}"
+        warn "\n  sudo rm #{migration_file}\n\n"
+      end
+    end
+  end
+end