Limit Atom feeds to 20 items by default, add pagination by max_id

(But there are no Atom feed pagination elements yet)

app/controllers/accounts_controller.rb

@@ -7,7 +7,7 @@ class AccountsController < ApplicationController
   def show
     respond_to do |format|
       format.html { @statuses = @account.statuses.order('id desc').with_includes.with_counters.paginate(page: params[:page], per_page: 10)}
-      format.atom { @entries  = @account.stream_entries.order('id desc').with_includes }
+      format.atom { @entries  = @account.stream_entries.order('id desc').with_includes.paginate_by_max_id(20, params[:max_id] || nil) }
     end
   end
 

app/models/stream_entry.rb

@@ -5,6 +5,7 @@ class StreamEntry < ActiveRecord::Base
   validates :account, :activity, presence: true
 
   scope :with_includes,      -> { includes(:activity) }
+  scope :paginate_by_max_id, -> (limit, max_id) { order('id desc').limit(limit).where(max_id.nil? ? '1=1' : ['id < ?', max_id]) }
 
   def object_type
     orphaned? ? :activity : (targeted? ? :activity : self.activity.object_type)

app/views/accounts/show.atom.ruby

@@ -15,7 +15,7 @@ Nokogiri::XML::Builder.new do |xml|
     link_hub       xml, Rails.configuration.x.hub_url
     link_salmon    xml, api_salmon_url(@account.id)
 
-    @entries.order('id desc').each do |stream_entry|
+    @entries.each do |stream_entry|
       entry(xml, false) do
         include_entry xml, stream_entry
       end