3 files changed, 67 insertions, 5 deletions
diff --git a/lib/banzai/filter/abstract_reference_filter.rb b/lib/banzai/filter/abstract_reference_filter.rb
index f21dbef216c..b8962379cb5 100644
--- a/lib/banzai/filter/abstract_reference_filter.rb
+++ b/lib/banzai/filter/abstract_reference_filter.rb
@@ -119,7 +119,7 @@ module Banzai
 
           elsif element_node?(node)
             yield_valid_link(node) do |link, text|
-              if ref_pattern && link =~ /\A#{ref_pattern}/
+              if ref_pattern && link =~ /\A#{ref_pattern}\z/
                 replace_link_node_with_href(node, link) do
                   object_link_filter(link, ref_pattern, link_text: text)
                 end
diff --git a/lib/banzai/filter/gollum_tags_filter.rb b/lib/banzai/filter/gollum_tags_filter.rb
index 7ce26db1b90..d08267a9d6c 100644
--- a/lib/banzai/filter/gollum_tags_filter.rb
+++ b/lib/banzai/filter/gollum_tags_filter.rb
@@ -118,7 +118,7 @@ module Banzai
         end
 
         if path
-          content_tag(:img, nil, src: path)
+          content_tag(:img, nil, src: path, class: 'gfm')
         end
       end
 
@@ -144,12 +144,18 @@ module Banzai
       # if it is not.
       def process_page_link_tag(parts)
         if parts.size == 1
-          url = parts[0].strip
+          reference = parts[0].strip
         else
-          name, url = *parts.compact.map(&:strip)
+          name, reference = *parts.compact.map(&:strip)
         end
 
-        content_tag(:a, name || url, href: url)
+        if url?(reference)
+          href = reference
+        else
+          href = ::File.join(project_wiki_base_path, reference)
+        end
+
+        content_tag(:a, name || reference, href: href, class: 'gfm')
       end
 
       def project_wiki
diff --git a/lib/banzai/filter/wiki_link_filter.rb b/lib/banzai/filter/wiki_link_filter.rb
new file mode 100644
index 00000000000..06d10c98501
--- /dev/null
+++ b/lib/banzai/filter/wiki_link_filter.rb
@@ -0,0 +1,56 @@
+require 'uri'
+
+module Banzai
+  module Filter
+    # HTML filter that "fixes" relative links to files in a repository.
+    #
+    # Context options:
+    #   :project_wiki
+    class WikiLinkFilter < HTML::Pipeline::Filter
+
+      def call
+        return doc unless project_wiki?
+
+        doc.search('a:not(.gfm)').each do |el|
+          process_link_attr el.attribute('href')
+        end
+
+        doc
+      end
+
+      protected
+
+      def project_wiki?
+        !context[:project_wiki].nil?
+      end
+
+      def process_link_attr(html_attr)
+        return if html_attr.blank? || file_reference?(html_attr)
+
+        uri = URI(html_attr.value)
+        if uri.relative? && uri.path.present?
+          html_attr.value = rebuild_wiki_uri(uri).to_s
+        end
+      rescue URI::Error
+        # noop
+      end
+
+      def rebuild_wiki_uri(uri)
+        uri.path = ::File.join(project_wiki_base_path, uri.path)
+        uri
+      end
+
+      def file_reference?(html_attr)
+        !File.extname(html_attr.value).blank?
+      end
+
+      def project_wiki
+        context[:project_wiki]
+      end
+
+      def project_wiki_base_path
+        project_wiki && project_wiki.wiki_base_path
+      end
+    end
+  end
+end