Backport changes from gitlab-org/gitlab-ee!998

Some changes in EE for the auditor user feature need
to be backported to CE to avoid merge conflicts. This
commit encapsulates all these backports.

app/policies/project_policy.rb

@@ -214,25 +214,7 @@ class ProjectPolicy < BasePolicy
   def anonymous_rules
     return unless project.public?
-    can! :read_project
-    can! :read_board
-    can! :read_list
-    can! :read_wiki
-    can! :read_label
-    can! :read_milestone
-    can! :read_project_snippet
-    can! :read_project_member
-    can! :read_merge_request
-    can! :read_note
-    can! :read_pipeline
-    can! :read_commit_status
-    can! :read_container_image
-    can! :download_code
-    can! :download_wiki_code
-    can! :read_cycle_analytics
-
-    # NOTE: may be overridden by IssuePolicy
-    can! :read_issue
+    base_readonly_access!
     # Allow to read builds by anonymous user if guests are allowed
     can! :read_build if project.public_builds?
@@ -265,4 +247,31 @@ class ProjectPolicy < BasePolicy
       :"admin_#{name}"
     ]
   end
+
+  private
+
+  # A base set of abilities for read-only users, which
+  # is then augmented as necessary for anonymous and other
+  # read-only users.
+  def base_readonly_access!
+    can! :read_project
+    can! :read_board
+    can! :read_list
+    can! :read_wiki
+    can! :read_label
+    can! :read_milestone
+    can! :read_project_snippet
+    can! :read_project_member
+    can! :read_merge_request
+    can! :read_note
+    can! :read_pipeline
+    can! :read_commit_status
+    can! :read_container_image
+    can! :download_code
+    can! :download_wiki_code
+    can! :read_cycle_analytics
+
+    # NOTE: may be overridden by IssuePolicy
+    can! :read_issue
+  end
 end

app/policies/project_snippet_policy.rb

@@ -3,7 +3,7 @@ class ProjectSnippetPolicy < BasePolicy
     can! :read_project_snippet if @subject.public?
     return unless @user
-    if @user && @subject.author == @user || @user.admin?
+    if @user && (@subject.author == @user || @user.admin?)
       can! :read_project_snippet
       can! :update_project_snippet
       can! :admin_project_snippet

app/views/projects/notes/_notes_with_form.html.haml

@@ -13,7 +13,7 @@
           = image_tag avatar_icon(current_user), alt: current_user.to_reference, class: 'avatar s40'
       .timeline-content.timeline-content-form
         = render "projects/notes/form", view: diff_view
-    - else
+    - elsif !current_user
       .disabled-comment.text-center
         .disabled-comment-text.inline
           Please