Merge branch 'master' into new-sidebar

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Conflicts:
	app/controllers/snippets_controller.rb

14 files changed, 1001 insertions, 312 deletions

diff --git a/lib/gitlab/google_code_import/importer.rb b/lib/gitlab/google_code_import/importer.rb
index b5e82563ff1..70bfe059776 100644
--- a/lib/gitlab/google_code_import/importer.rb
+++ b/lib/gitlab/google_code_import/importer.rb
@@ -30,7 +30,10 @@ module Gitlab
 
       def user_map
         @user_map ||= begin
-          user_map = Hash.new { |hash, user| Client.mask_email(user) }
+          user_map = Hash.new do |hash, user| 
+            # Replace ... by \.\.\., so `johnsm...@gmail.com` isn't autolinked.
+            Client.mask_email(user).sub("...", "\\.\\.\\.")
+          end
 
           import_data = project.import_data.try(:data)
           stored_user_map = import_data["user_map"] if import_data
@@ -203,25 +206,25 @@ module Gitlab
       end
 
       def linkify_issues(s)
-        s.gsub(/([Ii]ssue) ([0-9]+)/, '\1 #\2')
+        s = s.gsub(/([Ii]ssue) ([0-9]+)/, '\1 #\2')
+        s = s.gsub(/([Cc]omment) #([0-9]+)/, '\1 \2')
+        s
       end
 
       def escape_for_markdown(s)
-        s = s.gsub("*", "\\*")
-        s = s.gsub("#", "\\#")
+        # No headings and lists
+        s = s.gsub(/^#/, "\\#")
+        s = s.gsub(/^-/, "\\-")
+
+        # No inline code
         s = s.gsub("`", "\\`")
-        s = s.gsub(":", "\\:")
-        s = s.gsub("-", "\\-")
-        s = s.gsub("+", "\\+")
-        s = s.gsub("_", "\\_")
-        s = s.gsub("(", "\\(")
-        s = s.gsub(")", "\\)")
-        s = s.gsub("[", "\\[")
-        s = s.gsub("]", "\\]")
-        s = s.gsub("<", "\\<")
-        s = s.gsub(">", "\\>")
+
+        # Carriage returns make me sad
         s = s.gsub("\r", "")
+
+        # Markdown ignores single newlines, but we need them as <br />.
         s = s.gsub("\n", "  \n")
+
         s
       end
 
@@ -276,11 +279,18 @@ module Gitlab
         if raw_updates.has_key?("blockedOn")
           blocked_ons = raw_updates["blockedOn"].map do |raw_blocked_on|
             name, id = raw_blocked_on.split(":", 2)
-            if name == project.import_source
-              "##{id}"
-            else
-              "#{project.namespace.path}/#{name}##{id}"
-            end
+
+            deleted = name.start_with?("-") 
+            name = name[1..-1] if deleted
+
+            text =
+              if name == project.import_source
+                "##{id}"
+              else
+                "#{project.namespace.path}/#{name}##{id}"
+              end
+            text = "~~#{text}~~" if deleted
+            text
           end
           updates << "*Blocked on: #{blocked_ons.join(", ")}*"
         end
@@ -288,11 +298,18 @@ module Gitlab
         if raw_updates.has_key?("blocking")
           blockings = raw_updates["blocking"].map do |raw_blocked_on|
             name, id = raw_blocked_on.split(":", 2)
-            if name == project.import_source
-              "##{id}"
-            else
-              "#{project.namespace.path}/#{name}##{id}"
-            end
+            
+            deleted = name.start_with?("-") 
+            name = name[1..-1] if deleted
+
+            text =
+              if name == project.import_source
+                "##{id}"
+              else
+                "#{project.namespace.path}/#{name}##{id}"
+              end
+            text = "~~#{text}~~" if deleted
+            text
           end
           updates << "*Blocking: #{blockings.join(", ")}*"
         end
@@ -340,7 +357,7 @@ module Gitlab
 
       def format_issue_body(author, date, content, attachments)
         body = []
-        body << "*By #{author} on #{date}*"
+        body << "*By #{author} on #{date} (imported from Google Code)*"
         body << "---"
 
         if content.blank?
diff --git a/lib/gitlab/markdown.rb b/lib/gitlab/markdown.rb
index 47c456d8dc7..37b250d353e 100644
--- a/lib/gitlab/markdown.rb
+++ b/lib/gitlab/markdown.rb
@@ -1,5 +1,4 @@
 require 'html/pipeline'
-require 'html/pipeline/gitlab'
 
 module Gitlab
   # Custom parser for GitLab-flavored Markdown
@@ -10,11 +9,11 @@ module Gitlab
   # Supported reference formats are:
   #   * @foo for team members
   #   * #123 for issues
-  #   * #JIRA-123 for Jira issues
+  #   * JIRA-123 for Jira issues
   #   * !123 for merge requests
   #   * $123 for snippets
-  #   * 123456 for commits
-  #   * 123456...7890123 for commit ranges (comparisons)
+  #   * 1c002d for specific commit
+  #   * 1c002d...35cfb2 for commit ranges (comparisons)
   #
   # It also parses Emoji codes to insert images. See
   # http://www.emoji-cheat-sheet.com/ for a list of the supported icons.
@@ -30,10 +29,6 @@ module Gitlab
   #   >> gfm(":trollface:")
   #   => "<img alt=\":trollface:\" class=\"emoji\" src=\"/images/trollface.png" title=\":trollface:\" />
   module Markdown
-    include IssuesHelper
-
-    attr_reader :options, :html_options
-
     # Public: Parse the provided text with GitLab-Flavored Markdown
     #
     # text         - the source text
@@ -65,47 +60,24 @@ module Gitlab
         reference_only_path:  true
       )
 
-      @options      = options
-      @html_options = html_options
-
-      # TODO: add popups with additional information
+      pipeline = HTML::Pipeline.new(filters)
 
-      # Used markdown pipelines in GitLab:
-      # GitlabEmojiFilter - performs emoji replacement.
-      # SanitizationFilter - remove unsafe HTML tags and attributes
-      #
-      # see https://gitlab.com/gitlab-org/html-pipeline-gitlab for more filters
-      filters = [
-        HTML::Pipeline::Gitlab::GitlabEmojiFilter,
-        HTML::Pipeline::SanitizationFilter
-      ]
+      context = {
+        # SanitizationFilter
+        whitelist:       sanitization_whitelist,
 
-      whitelist = HTML::Pipeline::SanitizationFilter::WHITELIST
-      whitelist[:attributes][:all].push('class', 'id')
-      whitelist[:elements].push('span')
-
-      # Remove the rel attribute that the sanitize gem adds, and remove the
-      # href attribute if it contains inline javascript
-      fix_anchors = lambda do |env|
-        name, node = env[:node_name], env[:node]
-        if name == 'a'
-          node.remove_attribute('rel')
-          if node['href'] && node['href'].match('javascript:')
-            node.remove_attribute('href')
-          end
-        end
-      end
-      whitelist[:transformers].push(fix_anchors)
+        # EmojiFilter
+        asset_root:      Gitlab.config.gitlab.url,
+        asset_host:      Gitlab::Application.config.asset_host,
 
-      markdown_context = {
-              asset_root: Gitlab.config.gitlab.url,
-              asset_host: Gitlab::Application.config.asset_host,
-              whitelist: whitelist
+        # ReferenceFilter
+        current_user:    current_user,
+        only_path:       options[:reference_only_path],
+        project:         project,
+        reference_class: html_options[:class]
       }
 
-      markdown_pipeline = HTML::Pipeline::Gitlab.new(filters).pipeline
-
-      result = markdown_pipeline.call(text, markdown_context)
+      result = pipeline.call(text, context)
 
       save_options = 0
       if options[:xhtml]
@@ -114,21 +86,6 @@ module Gitlab
 
       text = result[:output].to_html(save_with: save_options)
 
-      # Extract pre blocks so they are not altered
-      # from http://github.github.com/github-flavored-markdown/
-      text.gsub!(%r{<pre>.*?</pre>|<code>.*?</code>}m) { |match| extract_piece(match) }
-      # Extract links with probably parsable hrefs
-      text.gsub!(%r{<a.*?>.*?</a>}m) { |match| extract_piece(match) }
-      # Extract images with probably parsable src
-      text.gsub!(%r{<img.*?>}m) { |match| extract_piece(match) }
-
-      text = parse(text, project)
-
-      # Insert pre block extractions
-      text.gsub!(/\{gfm-extraction-(\h{32})\}/) do
-        insert_piece($1)
-      end
-
       if options[:parse_tasks]
         text = parse_tasks(text)
       end
@@ -138,242 +95,53 @@ module Gitlab
 
     private
 
-    def extract_piece(text)
-      @extractions ||= {}
-
-      md5 = Digest::MD5.hexdigest(text)
-      @extractions[md5] = text
-      "{gfm-extraction-#{md5}}"
-    end
-
-    def insert_piece(id)
-      @extractions[id]
-    end
-
-    # Private: Parses text for references
+    # Filters used in our pipeline
     #
-    # text - Text to parse
+    # SanitizationFilter should come first so that all generated reference HTML
+    # goes through untouched.
     #
-    # Returns parsed text
-    def parse(text, project = @project)
-      parse_references(text, project) if project
-
-      text
-    end
-
-    NAME_STR = Gitlab::Regex::NAMESPACE_REGEX_STR
-    PROJ_STR = "(?<project>#{NAME_STR}/#{NAME_STR})"
-
-    REFERENCE_PATTERN = %r{
-      (?<prefix>\W)?                         # Prefix
-      (                                      # Reference
-         @(?<user>#{NAME_STR})               # User name
-        |~(?<label>\d+)                      # Label ID
-        |(?<issue>([A-Z\-]+-)\d+)            # JIRA Issue ID
-        |#{PROJ_STR}?\#(?<issue>([a-zA-Z\-]+-)?\d+) # Issue ID
-        |#{PROJ_STR}?!(?<merge_request>\d+)  # MR ID
-        |\$(?<snippet>\d+)                   # Snippet ID
-        |(#{PROJ_STR}@)?(?<commit_range>[\h]{6,40}\.{2,3}[\h]{6,40}) # Commit range
-        |(#{PROJ_STR}@)?(?<commit>[\h]{6,40}) # Commit ID
-        |(?<skip>gfm-extraction-[\h]{6,40})  # Skip gfm extractions. Otherwise will be parsed as commit
-      )
-      (?<suffix>\W)?                         # Suffix
-    }x.freeze
-
-    TYPES = [:user, :issue, :label, :merge_request, :snippet, :commit, :commit_range].freeze
-
-    def parse_references(text, project = @project)
-      # parse reference links
-      text.gsub!(REFERENCE_PATTERN) do |match|
-        type       = TYPES.select{|t| !$~[t].nil?}.first
-
-        actual_project = project
-        project_prefix = nil
-        project_path = $LAST_MATCH_INFO[:project]
-        if project_path
-          actual_project = ::Project.find_with_namespace(project_path)
-          actual_project = nil unless can?(current_user, :read_project, actual_project)
-          project_prefix = project_path
-        end
-
-        parse_result($LAST_MATCH_INFO, type,
-                     actual_project, project_prefix) || match
-      end
-    end
-
-    # Called from #parse_references.  Attempts to build a gitlab reference
-    # link.  Returns nil if +type+ is nil, if the match string is an HTML
-    # entity, if the reference is invalid, or if the matched text includes an
-    # invalid project path.
-    def parse_result(match_info, type, project, project_prefix)
-      prefix = match_info[:prefix]
-      suffix = match_info[:suffix]
-
-      return nil if html_entity?(prefix, suffix) || type.nil?
-      return nil if project.nil? && !project_prefix.nil?
-
-      identifier = match_info[type]
-      ref_link = reference_link(type, identifier, project, project_prefix)
-
-      if ref_link
-        "#{prefix}#{ref_link}#{suffix}"
-      else
-        nil
-      end
-    end
-
-    # Return true if the +prefix+ and +suffix+ indicate that the matched string
-    # is an HTML entity like &amp;
-    def html_entity?(prefix, suffix)
-      prefix && suffix && prefix[0] == '&' && suffix[-1] == ';'
+    # See https://gitlab.com/gitlab-org/html-pipeline-gitlab for more filters
+    def filters
+      [
+        HTML::Pipeline::SanitizationFilter,
+
+        Gitlab::Markdown::EmojiFilter,
+
+        Gitlab::Markdown::UserReferenceFilter,
+        Gitlab::Markdown::IssueReferenceFilter,
+        Gitlab::Markdown::ExternalIssueReferenceFilter,
+        Gitlab::Markdown::MergeRequestReferenceFilter,
+        Gitlab::Markdown::SnippetReferenceFilter,
+        Gitlab::Markdown::CommitRangeReferenceFilter,
+        Gitlab::Markdown::CommitReferenceFilter,
+        Gitlab::Markdown::LabelReferenceFilter,
+      ]
     end
 
-    # Private: Dispatches to a dedicated processing method based on reference
-    #
-    # reference  - Object reference ("@1234", "!567", etc.)
-    # identifier - Object identifier (Issue ID, SHA hash, etc.)
+    # Customize the SanitizationFilter whitelist
     #
-    # Returns string rendered by the processing method
-    def reference_link(type, identifier, project = @project, prefix_text = nil)
-      send("reference_#{type}", identifier, project, prefix_text)
-    end
-
-    def reference_user(identifier, project = @project, _ = nil)
-      link_options = html_options.merge(
-          class: "gfm gfm-project_member #{html_options[:class]}"
-        )
+    # - Allow `class` and `id` attributes on all elements
+    # - Allow `span` elements
+    # - Remove `rel` attributes from `a` elements
+    # - Remove `a` nodes with `javascript:` in the `href` attribute
+    def sanitization_whitelist
+      whitelist = HTML::Pipeline::SanitizationFilter::WHITELIST
+      whitelist[:attributes][:all].push('class', 'id')
+      whitelist[:elements].push('span')
 
-      if identifier == "all"
-        link_to(
-          "@all",
-          namespace_project_url(project.namespace, project, only_path: options[:reference_only_path]),
-          link_options
-        )
-      elsif namespace = Namespace.find_by(path: identifier)
-        url =
-          if namespace.is_a?(Group)
-            return nil unless can?(current_user, :read_group, namespace)
-            group_url(identifier, only_path: options[:reference_only_path])
-          else
-            user_url(identifier, only_path: options[:reference_only_path])
+      fix_anchors = lambda do |env|
+        name, node = env[:node_name], env[:node]
+        if name == 'a'
+          node.remove_attribute('rel')
+          if node['href'] && node['href'].match('javascript:')
+            node.remove_attribute('href')
           end
-
-        link_to("@#{identifier}", url, link_options)
-      end
-    end
-
-    def reference_label(identifier, project = @project, _ = nil)
-      if label = project.labels.find_by(id: identifier)
-        link_options = html_options.merge(
-          class: "gfm gfm-label #{html_options[:class]}"
-        )
-        link_to(
-          render_colored_label(label),
-          namespace_project_issues_path(project.namespace, project, label_name: label.name),
-          link_options
-        )
-      end
-    end
-
-    def reference_issue(identifier, project = @project, prefix_text = nil)
-      if project.default_issues_tracker?
-        if project.issue_exists? identifier
-          url = url_for_issue(identifier, project, only_path: options[:reference_only_path])
-          title = title_for_issue(identifier, project)
-          link_options = html_options.merge(
-            title: "Issue: #{title}",
-            class: "gfm gfm-issue #{html_options[:class]}"
-          )
-
-          link_to("#{prefix_text}##{identifier}", url, link_options)
-        end
-      else
-        if project.external_issue_tracker.present?
-          reference_external_issue(identifier, project,
-                                   prefix_text)
         end
       end
-    end
-
-    def reference_merge_request(identifier, project = @project, prefix_text = nil)
-      if merge_request = project.merge_requests.find_by(iid: identifier)
-        link_options = html_options.merge(
-          title: "Merge Request: #{merge_request.title}",
-          class: "gfm gfm-merge_request #{html_options[:class]}"
-        )
-        url = namespace_project_merge_request_url(project.namespace, project,
-                                                  merge_request,
-                                                  only_path: options[:reference_only_path])
-        link_to("#{prefix_text}!#{identifier}", url, link_options)
-      end
-    end
-
-    def reference_snippet(identifier, project = @project, _ = nil)
-      if snippet = project.snippets.find_by(id: identifier)
-        link_options = html_options.merge(
-          title: "Snippet: #{snippet.title}",
-          class: "gfm gfm-snippet #{html_options[:class]}"
-        )
-        link_to(
-          "$#{identifier}",
-          namespace_project_snippet_url(project.namespace, project, snippet,
-                                        only_path: options[:reference_only_path]),
-          link_options
-        )
-      end
-    end
-
-    def reference_commit(identifier, project = @project, prefix_text = nil)
-      if project.valid_repo? && commit = project.repository.commit(identifier)
-        link_options = html_options.merge(
-          title: commit.link_title,
-          class: "gfm gfm-commit #{html_options[:class]}"
-        )
-        prefix_text = "#{prefix_text}@" if prefix_text
-        link_to(
-          "#{prefix_text}#{identifier}",
-          namespace_project_commit_url( project.namespace, project, commit,
-                                        only_path: options[:reference_only_path]),
-          link_options
-        )
-      end
-    end
-
-    def reference_commit_range(identifier, project = @project, prefix_text = nil)
-      from_id, to_id = identifier.split(/\.{2,3}/, 2)
-
-      inclusive = identifier !~ /\.{3}/
-      from_id << "^" if inclusive
-
-      if project.valid_repo? &&
-          from = project.repository.commit(from_id) &&
-          to = project.repository.commit(to_id)
-
-        link_options = html_options.merge(
-          title: "Commits #{from_id} through #{to_id}",
-          class: "gfm gfm-commit_range #{html_options[:class]}"
-        )
-        prefix_text = "#{prefix_text}@" if prefix_text
 
-        link_to(
-          "#{prefix_text}#{identifier}",
-          namespace_project_compare_url(project.namespace, project,
-                                        from: from_id, to: to_id,
-                                        only_path: options[:reference_only_path]),
-          link_options
-        )
-      end
-    end
-
-    def reference_external_issue(identifier, project = @project, prefix_text = nil)
-      url = url_for_issue(identifier, project, only_path: options[:reference_only_path])
-      title = project.external_issue_tracker.title
+      whitelist[:transformers].push(fix_anchors)
 
-      link_options = html_options.merge(
-        title: "Issue in #{title}",
-        class: "gfm gfm-issue #{html_options[:class]}"
-      )
-      link_to("#{prefix_text}##{identifier}", url, link_options)
+      whitelist
     end
 
     # Turn list items that start with "[ ]" into HTML checkbox inputs.
diff --git a/lib/gitlab/markdown/commit_range_reference_filter.rb b/lib/gitlab/markdown/commit_range_reference_filter.rb
new file mode 100644
index 00000000000..1128c1bed7a
--- /dev/null
+++ b/lib/gitlab/markdown/commit_range_reference_filter.rb
@@ -0,0 +1,105 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces commit range references with links.
+    #
+    # This filter supports cross-project references.
+    class CommitRangeReferenceFilter < ReferenceFilter
+      include CrossProjectReference
+
+      # Public: Find commit range references in text
+      #
+      #   CommitRangeReferenceFilter.references_in(text) do |match, commit_range, project_ref|
+      #     "<a href=...>#{commit_range}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, the String commit range, and an optional String
+      # of the external project reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(COMMIT_RANGE_PATTERN) do |match|
+          yield match, $~[:commit_range], $~[:project]
+        end
+      end
+
+      def initialize(*args)
+        super
+
+        @commit_map = {}
+      end
+
+      # Pattern used to extract commit range references from text
+      #
+      # The beginning and ending SHA1 sums can be between 6 and 40 hex
+      # characters, and the range selection can be double- or triple-dot.
+      #
+      # This pattern supports cross-project references.
+      COMMIT_RANGE_PATTERN = /(#{PROJECT_PATTERN}@)?(?<commit_range>\h{6,40}\.{2,3}\h{6,40})/
+
+      def call
+        replace_text_nodes_matching(COMMIT_RANGE_PATTERN) do |content|
+          commit_range_link_filter(content)
+        end
+      end
+
+      # Replace commit range references in text with links to compare the commit
+      # ranges.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with commit range references replaced with links. All
+      # links have `gfm` and `gfm-commit_range` class names attached for
+      # styling.
+      def commit_range_link_filter(text)
+        self.class.references_in(text) do |match, commit_range, project_ref|
+          project = self.project_from_ref(project_ref)
+
+          from_id, to_id = split_commit_range(commit_range)
+
+          if valid_range?(project, from_id, to_id)
+            url = url_for_commit_range(project, from_id, to_id)
+
+            title = "Commits #{from_id} through #{to_id}"
+            klass = reference_class(:commit_range)
+
+            project_ref += '@' if project_ref
+
+            %(<a href="#{url}"
+                 title="#{title}"
+                 class="#{klass}">#{project_ref}#{commit_range}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      def split_commit_range(range)
+        from_id, to_id = range.split(/\.{2,3}/, 2)
+        from_id << "^" if range !~ /\.{3}/
+
+        [from_id, to_id]
+      end
+
+      def commit(id)
+        unless @commit_map[id]
+          @commit_map[id] = project.repository.commit(id)
+        end
+
+        @commit_map[id]
+      end
+
+      def valid_range?(project, from_id, to_id)
+        project && project.valid_repo? && commit(from_id) && commit(to_id)
+      end
+
+      def url_for_commit_range(project, from_id, to_id)
+        h = Rails.application.routes.url_helpers
+        h.namespace_project_compare_url(project.namespace, project,
+                                        from: from_id, to: to_id,
+                                        only_path: context[:only_path])
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/commit_reference_filter.rb b/lib/gitlab/markdown/commit_reference_filter.rb
new file mode 100644
index 00000000000..745de6402cf
--- /dev/null
+++ b/lib/gitlab/markdown/commit_reference_filter.rb
@@ -0,0 +1,80 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces commit references with links.
+    #
+    # This filter supports cross-project references.
+    class CommitReferenceFilter < ReferenceFilter
+      include CrossProjectReference
+
+      # Public: Find commit references in text
+      #
+      #   CommitReferenceFilter.references_in(text) do |match, commit, project_ref|
+      #     "<a href=...>#{commit}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, the String commit identifier, and an optional
+      # String of the external project reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(COMMIT_PATTERN) do |match|
+          yield match, $~[:commit], $~[:project]
+        end
+      end
+
+      # Pattern used to extract commit references from text
+      #
+      # The SHA1 sum can be between 6 and 40 hex characters.
+      #
+      # This pattern supports cross-project references.
+      COMMIT_PATTERN = /(#{PROJECT_PATTERN}@)?(?<commit>\h{6,40})/
+
+      def call
+        replace_text_nodes_matching(COMMIT_PATTERN) do |content|
+          commit_link_filter(content)
+        end
+      end
+
+      # Replace commit references in text with links to the commit specified.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with commit references replaced with links. All links
+      # have `gfm` and `gfm-commit` class names attached for styling.
+      def commit_link_filter(text)
+        self.class.references_in(text) do |match, commit_ref, project_ref|
+          project = self.project_from_ref(project_ref)
+
+          if commit = commit_from_ref(project, commit_ref)
+            url = url_for_commit(project, commit)
+
+            title = escape_once(commit.link_title)
+            klass = reference_class(:commit)
+
+            project_ref += '@' if project_ref
+
+            %(<a href="#{url}"
+                 title="#{title}"
+                 class="#{klass}">#{project_ref}#{commit_ref}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      def commit_from_ref(project, commit_ref)
+        if project && project.valid_repo?
+          project.repository.commit(commit_ref)
+        end
+      end
+
+      def url_for_commit(project, commit)
+        h = Rails.application.routes.url_helpers
+        h.namespace_project_commit_url(project.namespace, project, commit,
+                                        only_path: context[:only_path])
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/cross_project_reference.rb b/lib/gitlab/markdown/cross_project_reference.rb
new file mode 100644
index 00000000000..887c205cdc9
--- /dev/null
+++ b/lib/gitlab/markdown/cross_project_reference.rb
@@ -0,0 +1,32 @@
+module Gitlab
+  module Markdown
+    # Common methods for ReferenceFilters that support an optional cross-project
+    # reference.
+    module CrossProjectReference
+      NAMING_PATTERN  = Gitlab::Regex::NAMESPACE_REGEX_STR
+      PROJECT_PATTERN = "(?<project>#{NAMING_PATTERN}/#{NAMING_PATTERN})"
+
+      # Given a cross-project reference string, get the Project record
+      #
+      # Defaults to value of `context[:project]` if:
+      # * No reference is given OR
+      # * Reference given doesn't exist
+      #
+      # ref - String reference.
+      #
+      # Returns a Project, or nil if the reference can't be accessed
+      def project_from_ref(ref)
+        return context[:project] unless ref
+
+        other = Project.find_with_namespace(ref)
+        return nil unless other && user_can_reference_project?(other)
+        
+        other
+      end
+
+      def user_can_reference_project?(project, user = context[:current_user])
+        Ability.abilities.allowed?(user, :read_project, project)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/emoji_filter.rb b/lib/gitlab/markdown/emoji_filter.rb
new file mode 100644
index 00000000000..e239f766844
--- /dev/null
+++ b/lib/gitlab/markdown/emoji_filter.rb
@@ -0,0 +1,79 @@
+require 'gitlab_emoji'
+require 'html/pipeline/filter'
+require 'action_controller'
+
+module Gitlab
+  module Markdown
+    # HTML filter that replaces :emoji: with images.
+    #
+    # Based on HTML::Pipeline::EmojiFilter
+    #
+    # Context options:
+    #   :asset_root
+    #   :asset_host
+    class EmojiFilter < HTML::Pipeline::Filter
+      IGNORED_ANCESTOR_TAGS = %w(pre code tt).to_set
+
+      def call
+        doc.search('text()').each do |node|
+          content = node.to_html
+          next unless content.include?(':')
+          next if has_ancestor?(node, IGNORED_ANCESTOR_TAGS)
+
+          html = emoji_image_filter(content)
+
+          next if html == content
+
+          node.replace(html)
+        end
+
+        doc
+      end
+
+      # Replace :emoji: with corresponding images.
+      #
+      # text - String text to replace :emoji: in.
+      #
+      # Returns a String with :emoji: replaced with images.
+      def emoji_image_filter(text)
+        text.gsub(emoji_pattern) do |match|
+          name = $1
+          "<img class='emoji' title=':#{name}:' alt=':#{name}:' src='#{emoji_url(name)}' height='20' width='20' align='absmiddle' />"
+        end
+      end
+
+      private
+
+      def emoji_url(name)
+        emoji_path = "emoji/#{emoji_filename(name)}"
+        if context[:asset_host]
+          # Asset host is specified.
+          url_to_image(emoji_path)
+        elsif context[:asset_root]
+          # Gitlab url is specified
+          File.join(context[:asset_root], url_to_image(emoji_path))
+        else
+          # All other cases
+          url_to_image(emoji_path)
+        end
+      end
+
+      def url_to_image(image)
+        ActionController::Base.helpers.url_to_image(image)
+      end
+
+      # Build a regexp that matches all valid :emoji: names.
+      def self.emoji_pattern
+        @emoji_pattern ||= /:(#{Emoji.emojis_names.map { |name| Regexp.escape(name) }.join('|')}):/
+      end
+
+      def emoji_pattern
+        self.class.emoji_pattern
+      end
+
+      def emoji_filename(name)
+        "#{Emoji.emoji_filename(name)}.png"
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/external_issue_reference_filter.rb b/lib/gitlab/markdown/external_issue_reference_filter.rb
new file mode 100644
index 00000000000..0fc3f4cca06
--- /dev/null
+++ b/lib/gitlab/markdown/external_issue_reference_filter.rb
@@ -0,0 +1,63 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces external issue tracker references with links.
+    # References are ignored if the project doesn't use an external issue
+    # tracker.
+    class ExternalIssueReferenceFilter < ReferenceFilter
+      # Public: Find `JIRA-123` issue references in text
+      #
+      #   ExternalIssueReferenceFilter.references_in(text) do |match, issue|
+      #     "<a href=...>##{issue}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match and the String issue reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(ISSUE_PATTERN) do |match|
+          yield match, $~[:issue]
+        end
+      end
+
+      # Pattern used to extract `JIRA-123` issue references from text
+      ISSUE_PATTERN = /(?<issue>([A-Z\-]+-)\d+)/
+
+      def call
+        # Early return if the project isn't using an external tracker
+        return doc if project.nil? || project.default_issues_tracker?
+
+        replace_text_nodes_matching(ISSUE_PATTERN) do |content|
+          issue_link_filter(content)
+        end
+      end
+
+      # Replace `JIRA-123` issue references in text with links to the referenced
+      # issue's details page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `JIRA-123` references replaced with links. All
+      # links have `gfm` and `gfm-issue` class names attached for styling.
+      def issue_link_filter(text)
+        project = context[:project]
+
+        self.class.references_in(text) do |match, issue|
+          url = url_for_issue(issue, project, only_path: context[:only_path])
+
+          title = escape_once("Issue in #{project.external_issue_tracker.title}")
+          klass = reference_class(:issue)
+
+          %(<a href="#{url}"
+               title="#{title}"
+               class="#{klass}">#{issue}</a>)
+        end
+      end
+
+      def url_for_issue(*args)
+        IssuesHelper.url_for_issue(*args)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/issue_reference_filter.rb b/lib/gitlab/markdown/issue_reference_filter.rb
new file mode 100644
index 00000000000..c9267cc3e9d
--- /dev/null
+++ b/lib/gitlab/markdown/issue_reference_filter.rb
@@ -0,0 +1,74 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces issue references with links. References to
+    # issues that do not exist are ignored.
+    #
+    # This filter supports cross-project references.
+    class IssueReferenceFilter < ReferenceFilter
+      include CrossProjectReference
+
+      # Public: Find `#123` issue references in text
+      #
+      #   IssueReferenceFilter.references_in(text) do |match, issue, project_ref|
+      #     "<a href=...>##{issue}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, the Integer issue ID, and an optional String of
+      # the external project reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(ISSUE_PATTERN) do |match|
+          yield match, $~[:issue].to_i, $~[:project]
+        end
+      end
+
+      # Pattern used to extract `#123` issue references from text
+      #
+      # This pattern supports cross-project references.
+      ISSUE_PATTERN = /#{PROJECT_PATTERN}?\#(?<issue>([a-zA-Z\-]+-)?\d+)/
+
+      def call
+        replace_text_nodes_matching(ISSUE_PATTERN) do |content|
+          issue_link_filter(content)
+        end
+      end
+
+      # Replace `#123` issue references in text with links to the referenced
+      # issue's details page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `#123` references replaced with links. All links
+      # have `gfm` and `gfm-issue` class names attached for styling.
+      def issue_link_filter(text)
+        self.class.references_in(text) do |match, issue, project_ref|
+          project = self.project_from_ref(project_ref)
+
+          if project && project.issue_exists?(issue)
+            url = url_for_issue(issue, project, only_path: context[:only_path])
+
+            title = escape_once("Issue: #{title_for_issue(issue, project)}")
+            klass = reference_class(:issue)
+
+            %(<a href="#{url}"
+                 title="#{title}"
+                 class="#{klass}">#{project_ref}##{issue}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      def url_for_issue(*args)
+        IssuesHelper.url_for_issue(*args)
+      end
+
+      def title_for_issue(*args)
+        IssuesHelper.title_for_issue(*args)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/label_reference_filter.rb b/lib/gitlab/markdown/label_reference_filter.rb
new file mode 100644
index 00000000000..4c21192c0d3
--- /dev/null
+++ b/lib/gitlab/markdown/label_reference_filter.rb
@@ -0,0 +1,94 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces label references with links.
+    class LabelReferenceFilter < ReferenceFilter
+      # Public: Find label references in text
+      #
+      #   LabelReferenceFilter.references_in(text) do |match, id, name|
+      #     "<a href=...>#{Label.find(id)}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, an optional Integer label ID, and an optional
+      # String label name.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(LABEL_PATTERN) do |match|
+          yield match, $~[:label_id].to_i, $~[:label_name]
+        end
+      end
+
+      # Pattern used to extract label references from text
+      #
+      # TODO (rspeicher): Limit to double quotes (meh) or disallow single quotes in label names (bad).
+      LABEL_PATTERN = %r{
+        ~(
+          (?<label_id>\d+)   | # Integer-based label ID, or
+          (?<label_name>
+            [A-Za-z0-9_-]+   | # String-based single-word label title
+            ['"][^&\?,]+['"]   # String-based multi-word label surrounded in quotes
+          )
+        )
+      }x
+
+      def call
+        replace_text_nodes_matching(LABEL_PATTERN) do |content|
+          label_link_filter(content)
+        end
+      end
+
+      # Replace label references in text with links to the label specified.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with label references replaced with links. All links
+      # have `gfm` and `gfm-label` class names attached for styling.
+      def label_link_filter(text)
+        project = context[:project]
+
+        self.class.references_in(text) do |match, id, name|
+          params = label_params(id, name)
+
+          if label = project.labels.find_by(params)
+            url = url_for_label(project, label)
+
+            klass = reference_class(:label)
+
+            %(<a href="#{url}" class="#{klass}">#{render_colored_label(label)}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      def url_for_label(project, label)
+        h = Rails.application.routes.url_helpers
+        h.namespace_project_issues_path(project.namespace, project,
+                                        label_name: label.name,
+                                        only_path: context[:only_path])
+      end
+
+      def render_colored_label(label)
+        LabelsHelper.render_colored_label(label)
+      end
+
+      # Parameters to pass to `Label.find_by` based on the given arguments
+      #
+      # id   - Integer ID to pass. If present, returns {id: id}
+      # name - String name to pass. If `id` is absent, finds by name without
+      #        surrounding quotes.
+      #
+      # Returns a Hash.
+      def label_params(id, name)
+        if id > 0
+          { id: id }
+        else
+          # TODO (rspeicher): Don't strip single quotes if we decide to only use double quotes for surrounding.
+          { name: name.tr('\'"', '') }
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/merge_request_reference_filter.rb b/lib/gitlab/markdown/merge_request_reference_filter.rb
new file mode 100644
index 00000000000..40239523cda
--- /dev/null
+++ b/lib/gitlab/markdown/merge_request_reference_filter.rb
@@ -0,0 +1,73 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces merge request references with links. References
+    # to merge requests that do not exist are ignored.
+    #
+    # This filter supports cross-project references.
+    class MergeRequestReferenceFilter < ReferenceFilter
+      include CrossProjectReference
+
+      # Public: Find `!123` merge request references in text
+      #
+      #   MergeRequestReferenceFilter.references_in(text) do |match, merge_request, project_ref|
+      #     "<a href=...>##{merge_request}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, the Integer merge request ID, and an optional
+      # String of the external project reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(MERGE_REQUEST_PATTERN) do |match|
+          yield match, $~[:merge_request].to_i, $~[:project]
+        end
+      end
+
+      # Pattern used to extract `!123` merge request references from text
+      #
+      # This pattern supports cross-project references.
+      MERGE_REQUEST_PATTERN = /#{PROJECT_PATTERN}?!(?<merge_request>\d+)/
+
+      def call
+        replace_text_nodes_matching(MERGE_REQUEST_PATTERN) do |content|
+          merge_request_link_filter(content)
+        end
+      end
+
+      # Replace `!123` merge request references in text with links to the
+      # referenced merge request's details page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `!123` references replaced with links. All links
+      # have `gfm` and `gfm-merge_request` class names attached for styling.
+      def merge_request_link_filter(text)
+        self.class.references_in(text) do |match, id, project_ref|
+          project = self.project_from_ref(project_ref)
+
+          if project && merge_request = project.merge_requests.find_by(iid: id)
+            title = escape_once("Merge Request: #{merge_request.title}")
+            klass = reference_class(:merge_request)
+
+            url = url_for_merge_request(merge_request, project)
+
+            %(<a href="#{url}"
+                 title="#{title}"
+                 class="#{klass}">#{project_ref}!#{id}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      # TODO (rspeicher): Cleanup
+      def url_for_merge_request(mr, project)
+        h = Rails.application.routes.url_helpers
+        h.namespace_project_merge_request_url(project.namespace, project, mr,
+                                            only_path: context[:only_path])
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/reference_filter.rb b/lib/gitlab/markdown/reference_filter.rb
new file mode 100644
index 00000000000..26663c8d990
--- /dev/null
+++ b/lib/gitlab/markdown/reference_filter.rb
@@ -0,0 +1,76 @@
+require 'active_support/core_ext/string/output_safety'
+require 'html/pipeline'
+
+module Gitlab
+  module Markdown
+    # Base class for GitLab Flavored Markdown reference filters.
+    #
+    # References within <pre>, <code>, <a>, and <style> elements are ignored.
+    #
+    # Context options:
+    #   :project (required) - Current project, ignored if reference is cross-project.
+    #   :reference_class    - Custom CSS class added to reference links.
+    #   :only_path          - Generate path-only links.
+    #
+    class ReferenceFilter < HTML::Pipeline::Filter
+      def escape_once(html)
+        ERB::Util.html_escape_once(html)
+      end
+
+      # Don't look for references in text nodes that are children of these
+      # elements.
+      IGNORE_PARENTS = %w(pre code a style).to_set
+
+      def ignored_ancestry?(node)
+        has_ancestor?(node, IGNORE_PARENTS)
+      end
+
+      def project
+        context[:project]
+      end
+
+      def reference_class(type)
+        "gfm gfm-#{type} #{context[:reference_class]}".strip
+      end
+
+      # Iterate through the document's text nodes, yielding the current node's
+      # content if:
+      #
+      # * The `project` context value is present AND
+      # * The node's content matches `pattern` AND
+      # * The node is not an ancestor of an ignored node type
+      #
+      # pattern - Regex pattern against which to match the node's content
+      #
+      # Yields the current node's String contents. The result of the block will
+      # replace the node's existing content and update the current document.
+      #
+      # Returns the updated Nokogiri::XML::Document object.
+      def replace_text_nodes_matching(pattern)
+        return doc if project.nil?
+
+        doc.search('text()').each do |node|
+          content = node.to_html
+
+          next unless content.match(pattern)
+          next if ignored_ancestry?(node)
+
+          html = yield content
+
+          next if html == content
+
+          node.replace(html)
+        end
+
+        doc
+      end
+
+      # Ensure that a :project key exists in context
+      #
+      # Note that while the key might exist, its value could be nil!
+      def validate
+        needs :project
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/snippet_reference_filter.rb b/lib/gitlab/markdown/snippet_reference_filter.rb
new file mode 100644
index 00000000000..ada67de992b
--- /dev/null
+++ b/lib/gitlab/markdown/snippet_reference_filter.rb
@@ -0,0 +1,72 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces snippet references with links. References to
+    # snippets that do not exist are ignored.
+    #
+    # This filter supports cross-project references.
+    class SnippetReferenceFilter < ReferenceFilter
+      include CrossProjectReference
+
+      # Public: Find `$123` snippet references in text
+      #
+      #   SnippetReferenceFilter.references_in(text) do |match, snippet|
+      #     "<a href=...>$#{snippet}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, the Integer snippet ID, and an optional String
+      # of the external project reference.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(SNIPPET_PATTERN) do |match|
+          yield match, $~[:snippet].to_i, $~[:project]
+        end
+      end
+
+      # Pattern used to extract `$123` snippet references from text
+      #
+      # This pattern supports cross-project references.
+      SNIPPET_PATTERN = /#{PROJECT_PATTERN}?\$(?<snippet>\d+)/
+
+      def call
+        replace_text_nodes_matching(SNIPPET_PATTERN) do |content|
+          snippet_link_filter(content)
+        end
+      end
+
+      # Replace `$123` snippet references in text with links to the referenced
+      # snippets's details page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `$123` references replaced with links. All links
+      # have `gfm` and `gfm-snippet` class names attached for styling.
+      def snippet_link_filter(text)
+        self.class.references_in(text) do |match, id, project_ref|
+          project = self.project_from_ref(project_ref)
+
+          if project && snippet = project.snippets.find_by(id: id)
+            title = escape_once("Snippet: #{snippet.title}")
+            klass = reference_class(:snippet)
+
+            url = url_for_snippet(snippet, project)
+
+            %(<a href="#{url}"
+                 title="#{title}"
+                 class="#{klass}">#{project_ref}$#{id}</a>)
+          else
+            match
+          end
+        end
+      end
+
+      def url_for_snippet(snippet, project)
+        h = Rails.application.routes.url_helpers
+        h.namespace_project_snippet_url(project.namespace, project, snippet,
+                                        only_path: context[:only_path])
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/markdown/user_reference_filter.rb b/lib/gitlab/markdown/user_reference_filter.rb
new file mode 100644
index 00000000000..5fc8ed55fe2
--- /dev/null
+++ b/lib/gitlab/markdown/user_reference_filter.rb
@@ -0,0 +1,92 @@
+module Gitlab
+  module Markdown
+    # HTML filter that replaces user or group references with links.
+    #
+    # A special `@all` reference is also supported.
+    class UserReferenceFilter < ReferenceFilter
+      # Public: Find `@user` user references in text
+      #
+      #   UserReferenceFilter.references_in(text) do |match, username|
+      #     "<a href=...>@#{user}</a>"
+      #   end
+      #
+      # text - String text to search.
+      #
+      # Yields the String match, and the String user name.
+      #
+      # Returns a String replaced with the return of the block.
+      def self.references_in(text)
+        text.gsub(USER_PATTERN) do |match|
+          yield match, $~[:user]
+        end
+      end
+
+      # Pattern used to extract `@user` user references from text
+      USER_PATTERN = /@(?<user>#{Gitlab::Regex::NAMESPACE_REGEX_STR})/
+
+      def call
+        replace_text_nodes_matching(USER_PATTERN) do |content|
+          user_link_filter(content)
+        end
+      end
+
+      # Replace `@user` user references in text with links to the referenced
+      # user's profile page.
+      #
+      # text - String text to replace references in.
+      #
+      # Returns a String with `@user` references replaced with links. All links
+      # have `gfm` and `gfm-project_member` class names attached for styling.
+      def user_link_filter(text)
+        project = context[:project]
+
+        self.class.references_in(text) do |match, user|
+          klass = reference_class(:project_member)
+
+          if user == 'all'
+            url = link_to_all(project)
+
+            %(<a href="#{url}" class="#{klass}">@#{user}</a>)
+          elsif namespace = Namespace.find_by(path: user)
+            if namespace.is_a?(Group)
+              if user_can_reference_group?(namespace)
+                url = group_url(user, only_path: context[:only_path])
+                %(<a href="#{url}" class="#{klass}">@#{user}</a>)
+              else
+                match
+              end
+            else
+              url = user_url(user, only_path: context[:only_path])
+              %(<a href="#{url}" class="#{klass}">@#{user}</a>)
+            end
+          else
+            match
+          end
+        end
+      end
+
+      private
+
+      def urls
+        Rails.application.routes.url_helpers
+      end
+
+      def group_url(*args)
+        urls.group_url(*args)
+      end
+
+      def user_url(*args)
+        urls.user_url(*args)
+      end
+
+      def link_to_all(project)
+        urls.namespace_project_url(project.namespace, project,
+                                   only_path: context[:only_path])
+      end
+
+      def user_can_reference_group?(group)
+        Ability.abilities.allowed?(context[:current_user], :read_group, group)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/reference_extractor.rb b/lib/gitlab/reference_extractor.rb
index a502a8fe9cd..34aae384355 100644
--- a/lib/gitlab/reference_extractor.rb
+++ b/lib/gitlab/reference_extractor.rb
@@ -3,8 +3,6 @@ module Gitlab
   class ReferenceExtractor
     attr_accessor :project, :current_user, :references
 
-    include ::Gitlab::Markdown
-
     def initialize(project, current_user = nil)
       @project = project
       @current_user = current_user
@@ -34,7 +32,7 @@ module Gitlab
           project.team.members.flatten
         elsif namespace = Namespace.find_by(path: identifier)
           if namespace.is_a?(Group)
-            namespace.users
+            namespace.users if can?(current_user, :read_group, namespace)
           else
             namespace.owner
           end
@@ -87,6 +85,72 @@ module Gitlab
 
     private
 
+    NAME_STR = Gitlab::Regex::NAMESPACE_REGEX_STR
+    PROJ_STR = "(?<project>#{NAME_STR}/#{NAME_STR})"
+
+    REFERENCE_PATTERN = %r{
+      (?<prefix>\W)?                         # Prefix
+      (                                      # Reference
+         @(?<user>#{NAME_STR})               # User name
+        |~(?<label>\d+)                      # Label ID
+        |(?<issue>([A-Z\-]+-)\d+)            # JIRA Issue ID
+        |#{PROJ_STR}?\#(?<issue>([a-zA-Z\-]+-)?\d+) # Issue ID
+        |#{PROJ_STR}?!(?<merge_request>\d+)  # MR ID
+        |\$(?<snippet>\d+)                   # Snippet ID
+        |(#{PROJ_STR}@)?(?<commit_range>[\h]{6,40}\.{2,3}[\h]{6,40}) # Commit range
+        |(#{PROJ_STR}@)?(?<commit>[\h]{6,40}) # Commit ID
+      )
+      (?<suffix>\W)?                         # Suffix
+    }x.freeze
+
+    TYPES = %i(user issue label merge_request snippet commit commit_range).freeze
+
+    def parse_references(text, project = @project)
+      # parse reference links
+      text.gsub!(REFERENCE_PATTERN) do |match|
+        type = TYPES.detect { |t| $~[t].present? }
+
+        actual_project = project
+        project_prefix = nil
+        project_path = $LAST_MATCH_INFO[:project]
+        if project_path
+          actual_project = ::Project.find_with_namespace(project_path)
+          actual_project = nil unless can?(current_user, :read_project, actual_project)
+          project_prefix = project_path
+        end
+
+        parse_result($LAST_MATCH_INFO, type,
+                     actual_project, project_prefix) || match
+      end
+    end
+
+    # Called from #parse_references.  Attempts to build a gitlab reference
+    # link.  Returns nil if +type+ is nil, if the match string is an HTML
+    # entity, if the reference is invalid, or if the matched text includes an
+    # invalid project path.
+    def parse_result(match_info, type, project, project_prefix)
+      prefix = match_info[:prefix]
+      suffix = match_info[:suffix]
+
+      return nil if html_entity?(prefix, suffix) || type.nil?
+      return nil if project.nil? && !project_prefix.nil?
+
+      identifier = match_info[type]
+      ref_link = reference_link(type, identifier, project, project_prefix)
+
+      if ref_link
+        "#{prefix}#{ref_link}#{suffix}"
+      else
+        nil
+      end
+    end
+
+    # Return true if the +prefix+ and +suffix+ indicate that the matched string
+    # is an HTML entity like &amp;
+    def html_entity?(prefix, suffix)
+      prefix && suffix && prefix[0] == '&' && suffix[-1] == ';'
+    end
+
     def reference_link(type, identifier, project, _)
       references[type] << [project, identifier]
     end