Add auxiliary viewer for CONTRIBUTING

app/helpers/blob_helper.rb

@@ -278,4 +278,19 @@ module BlobHelper
     options
   end
+
+  def contribution_options(project)
+    options = []
+
+    if can?(current_user, :create_issue, project)
+      options << link_to("submit an issue", new_namespace_project_issue_path(project.namespace, project))
+    end
+
+    merge_project = can?(current_user, :create_merge_request, project) ? project : (current_user && current_user.fork_of(project))
+    if merge_project
+      options << link_to("create a merge request", new_namespace_project_merge_request_path(project.namespace, project))
+    end
+
+    options
+  end
 end

app/models/blob.rb

@@ -39,7 +39,9 @@ class Blob < SimpleDelegator
   AUXILIARY_VIEWERS = [
     BlobViewer::GitlabCiYml,
     BlobViewer::RouteMap,
-    BlobViewer::License
+
+    BlobViewer::License,
+    BlobViewer::Contributing
   ].freeze
   attr_reader :project

app/models/blob_viewer/contributing.rb

+module BlobViewer
+  class Contributing < Base
+    include Auxiliary
+    include Static
+
+    self.partial_name = 'contributing'
+    self.file_types = %i(contributing)
+    self.binary = false
+  end
+end

app/views/projects/blob/viewers/_contributing.html.haml

+= icon('book fw')
+After you've reviewed these contribution guidelines, you'll be all set to
+
+- options = contribution_options(viewer.project)
+- if options.any?
+  = succeed '.' do
+    = options.to_sentence(two_words_connector: ' or ', last_word_connector: ', or ').html_safe
+- else
+  contribute to this project.