blog/_src/_plugins/cat_pagination.rb

#
# https://gist.github.com/runemadsen/6263974
#
# modified
#

module Jekyll
  module Paginate

    class Pagination < Generator
      def generate(site)
      end
    end

    class CategoryPages < Generator

      safe true

      def generate(site)

        site.pages.dup.each do |page|
          paginate(site, page) if CategoryPager.pagination_enabled?(site.config, page)
        end

      end

      def paginate(site, page)

        # sort categories by descending date of publish
        category_posts = site.categories[page.data['category']].sort_by { |p| -p.date.to_f }

        # calculate total number of pages
        pages = CategoryPager.calculate_pages(category_posts, site.config['paginate'].to_i)

        # iterate over the total number of pages and create a physical page for each
        (1..pages).each do |num_page|

          # the CategoryPager handles the paging and category data
          pager = CategoryPager.new(site, num_page, category_posts, page.data['category'], pages)

          if num_page > 1
            newpage = Page.new(site, site.source, page.dir, page.name)
            newpage.pager = pager
            newpage.dir = File.join(page.dir, "/page/#{num_page}")
            site.pages << newpage
          else
            page.pager = pager
          end

        end
      end

    end

    class CategoryPager < Pager

      attr_reader :category

      def self.pagination_enabled?(config, page)
        page.name == 'index.html' && page.data.key?('category') && !config['paginate'].nil?
      end

      # same as the base class, but includes the category value
      def initialize(site, page, all_posts, category, num_pages = nil)
        @category = category
        super site, page, all_posts, num_pages
      end

      # use the original to_liquid method, but add in category info
      alias_method :original_to_liquid, :to_liquid
      def to_liquid
        x = original_to_liquid
        x['category'] = @category
        x
      end

    end

  end
end