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diff --git a/lib/banzai/filter/gollum_tags_filter.rb b/lib/banzai/filter/gollum_tags_filter.rb
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+++ b/lib/banzai/filter/gollum_tags_filter.rb
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+require 'banzai'
+require 'html/pipeline/filter'
+
+module Banzai
+  module Filter
+    # HTML Filter for parsing Gollum's tags in HTML. It's only parses the
+    # following tags:
+    #
+    # - Link to internal pages:
+    #
+    #   * [[Bug Reports]]
+    #   * [[How to Contribute|Contributing]]
+    #
+    # - Link to external resources:
+    #
+    #   * [[http://en.wikipedia.org/wiki/Git_(software)]]
+    #   * [[Git|http://en.wikipedia.org/wiki/Git_(software)]]
+    #
+    # - Link internal images, the special attributes will be ignored:
+    #
+    #   * [[images/logo.png]]
+    #   * [[images/logo.png|alt=Logo]]
+    #
+    # - Link external images, the special attributes will be ignored:
+    #
+    #   * [[http://example.com/images/logo.png]]
+    #   * [[http://example.com/images/logo.png|alt=Logo]]
+    #
+    # Based on Gollum::Filter::Tags
+    #
+    # Context options:
+    #   :project_wiki (required) - Current project wiki.
+    #
+    class GollumTagsFilter < HTML::Pipeline::Filter
+      include ActionView::Helpers::TagHelper
+
+      # Pattern to match tags content that should be parsed in HTML.
+      #
+      # Gollum's tags have been made to resemble the tags of other markups,
+      # especially MediaWiki. The basic syntax is:
+      #
+      # [[tag]]
+      #
+      # Some tags will accept attributes which are separated by pipe
+      # symbols.Some attributes must precede the tag and some must follow it:
+      #
+      # [[prefix-attribute|tag]]
+      # [[tag|suffix-attribute]]
+      #
+      # See https://github.com/gollum/gollum/wiki
+      #
+      # Rubular: http://rubular.com/r/7dQnE5CUCH
+      TAGS_PATTERN = %r{\[\[(.+?)\]\]}
+
+      # Pattern to match allowed image extensions
+      ALLOWED_IMAGE_EXTENSIONS = %r{.+(jpg|png|gif|svg|bmp)\z}i
+
+      def call
+        search_text_nodes(doc).each do |node|
+          content = node.content
+
+          next unless content.match(TAGS_PATTERN)
+
+          html = process_tag($1)
+
+          if html && html != node.content
+            node.replace(html)
+          end
+        end
+
+        doc
+      end
+
+      private
+
+      # Process a single tag into its final HTML form.
+      #
+      # tag - The String tag contents (the stuff inside the double brackets).
+      #
+      # Returns the String HTML version of the tag.
+      def process_tag(tag)
+        parts = tag.split('|')
+
+        return if parts.size.zero?
+
+        process_image_tag(parts) || process_page_link_tag(parts)
+      end
+
+      # Attempt to process the tag as an image tag.
+      #
+      # tag - The String tag contents (the stuff inside the double brackets).
+      #
+      # Returns the String HTML if the tag is a valid image tag or nil
+      # if it is not.
+      def process_image_tag(parts)
+        content = parts[0].strip
+
+        return unless image?(content)
+
+        if url?(content)
+          path = content
+        elsif file = project_wiki.find_file(content)
+          path = ::File.join project_wiki_base_path, file.path
+        end
+
+        if path
+          content_tag(:img, nil, src: path)
+        end
+      end
+
+      def image?(path)
+        path =~ ALLOWED_IMAGE_EXTENSIONS
+      end
+
+      def url?(path)
+        path.start_with?(*%w(http https))
+      end
+
+      # Attempt to process the tag as a page link tag.
+      #
+      # tag - The String tag contents (the stuff inside the double brackets).
+      #
+      # Returns the String HTML if the tag is a valid page link tag or nil
+      # if it is not.
+      def process_page_link_tag(parts)
+        if parts.size == 1
+          url = parts[0].strip
+        else
+          name, url = *parts.compact.map(&:strip)
+        end
+
+        content_tag(:a, name || url, href: url)
+      end
+
+      def project_wiki
+        context[:project_wiki]
+      end
+
+      def project_wiki_base_path
+        project_wiki && project_wiki.wiki_base_path
+      end
+
+      # Ensure that a :project_wiki key exists in context
+      #
+      # Note that while the key might exist, its value could be nil!
+      def validate
+        needs :project_wiki
+      end
+    end
+  end
+end