Add GFM helper

app/helpers/application_helper.rb

@@ -42,6 +42,74 @@ module ApplicationHelper
     grouped_options_for_select(options, @ref || @project.default_branch)
   end
 
+  def gfm(text, html_options = {})
+    return text if text.nil?
+
+    # Extract pre blocks
+    # from http://github.github.com/github-flavored-markdown/
+    extractions = {}
+    text.gsub!(%r{<pre>.*?</pre>|<code>.*?</code>}m) do |match|
+      md5 = Digest::MD5.hexdigest(match)
+      extractions[md5] = match
+      "{gfm-extraction-#{md5}}"
+    end
+
+    # match     1    2 3               4     5            6
+    text.gsub!(/(\W)?(@([\w\._]+)|[#!$](\d+)|([\h]{6,40}))(\W)?/) do |match|
+      prefix    = $1
+      reference = $2
+      user_name = $3
+      issue_id  = $4
+      merge_request_id = $4
+      snippet_id = $4
+      commit_id = $5
+      suffix    = $6
+
+      # TODO: add popups with additional information
+      ref_link = case reference
+
+                  # team member: @foo
+                  when /^@/
+                    user = @project.users.where(:name => user_name).first
+                    member = @project.users_projects.where(:user_id => user).first if user
+                    link_to("@#{user_name}", project_team_member_path(@project, member), html_options.merge(:class => "gfm gfm-team_member #{html_options[:class]}")) if member
+
+                  # issue: #123
+                  when /^#/
+                    # avoid HTML entities
+                    unless prefix.try(:end_with?, "&") && suffix.try(:start_with?, ";")
+                      issue = @project.issues.where(:id => issue_id).first
+                      link_to("##{issue_id}", project_issue_path(@project, issue), html_options.merge(:title => "Issue: #{issue.title}", :class => "gfm gfm-issue #{html_options[:class]}")) if issue
+                    end
+
+                  # merge request: !123
+                  when /^!/
+                    merge_request = @project.merge_requests.where(:id => merge_request_id).first
+                    link_to("!#{merge_request_id}", project_merge_request_path(@project, merge_request), html_options.merge(:title => "Merge Request: #{merge_request.title}", :class => "gfm gfm-merge_request #{html_options[:class]}")) if merge_request
+
+                  # snippet: $123
+                  when /^\$/
+                    snippet = @project.snippets.where(:id => snippet_id).first
+                    link_to("$#{snippet_id}", project_snippet_path(@project, snippet), html_options.merge(:title => "Snippet: #{snippet.title}", :class => "gfm gfm-snippet #{html_options[:class]}")) if snippet
+
+                  # commit: 123456...
+                  when /^\h/
+                    commit = @project.commit(commit_id)
+                    link_to(commit_id, project_commit_path(@project, :id => commit.id), html_options.merge(:title => "Commit: #{commit.author_name} - #{CommitDecorator.new(commit).title}", :class => "gfm gfm-commit #{html_options[:class]}")) if commit
+
+                  end # case
+
+      ref_link.nil? ? match : "#{prefix}#{ref_link}#{suffix}"
+    end # gsub
+
+    # Insert pre block extractions
+    text.gsub!(/\{gfm-extraction-(\h{32})\}/) do
+      extractions[$1]
+    end
+
+    text.html_safe
+  end
+
   def markdown(text)
     @__renderer ||= Redcarpet::Markdown.new(Redcarpet::Render::GitlabHTML.new(self, filter_html: true), {
       no_intra_emphasis: true,