Add auxiliary viewer for README

app/models/blob.rb

@@ -40,6 +40,7 @@ class Blob < SimpleDelegator
     BlobViewer::GitlabCiYml,
     BlobViewer::RouteMap,
 
+    BlobViewer::Readme,
     BlobViewer::License,
     BlobViewer::Contributing,
     BlobViewer::Changelog

app/models/blob_viewer/auxiliary.rb

@@ -2,11 +2,17 @@ module BlobViewer
   module Auxiliary
     extend ActiveSupport::Concern
 
+    include Gitlab::Allowable
+
     included do
       self.loading_partial_name = 'loading_auxiliary'
       self.type = :auxiliary
       self.overridable_max_size = 100.kilobytes
       self.max_size = 100.kilobytes
     end
+
+    def visible_to?(current_user)
+      true
+    end
   end
 end

app/models/blob_viewer/readme.rb

+module BlobViewer
+  class Readme < Base
+    include Auxiliary
+    include Static
+
+    self.partial_name = 'readme'
+    self.file_types = %i(readme)
+    self.binary = false
+
+    def visible_to?(current_user)
+      can?(current_user, :read_wiki, project)
+    end
+  end
+end

app/views/projects/blob/_auxiliary_viewer.html.haml

+- blob = local_assigns.fetch(:blob)
+- auxiliary_viewer = blob.auxiliary_viewer
+- if auxiliary_viewer && auxiliary_viewer.render_error.nil? && auxiliary_viewer.visible_to?(current_user)
+  .well-segment.blob-auxiliary-viewer
+    = render 'projects/blob/viewer', viewer: auxiliary_viewer

app/views/projects/blob/_blob.html.haml

@@ -6,10 +6,7 @@
       - blob_commit = @repository.last_commit_for_path(@commit.id, blob.path)
       = render blob_commit, project: @project, ref: @ref
 
-  - auxiliary_viewer = blob.auxiliary_viewer
-  - if auxiliary_viewer && !auxiliary_viewer.render_error
-    .well-segment.blob-auxiliary-viewer
-      = render 'projects/blob/viewer', viewer: auxiliary_viewer
+  = render "projects/blob/auxiliary_viewer", blob: blob
 
 #blob-content-holder.blob-content-holder
   %article.file-holder

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

+= icon('info-circle fw')
+= succeed '.' do
+  To learn more about this project, read
+  = link_to "the wiki", namespace_project_wikis_path(viewer.project.namespace, viewer.project)