wikis: add "tag history", "wiki history", "what links here" sidebar options.

app/models/wiki_page.rb

@@ -76,6 +76,10 @@ class WikiPage < ApplicationRecord
         q = q.tag_matches(params[:tag])
       end
 
+      if params[:linked_to].present?
+        q = q.where(id: DtextLink.wiki_link.where(link_target: params[:linked_to]).select(:model_id))
+      end
+
       if params[:hide_deleted].to_s.truthy?
         q = q.where("is_deleted = false")
       end
@@ -165,6 +169,10 @@ class WikiPage < ApplicationRecord
     title.starts_with?(*META_WIKIS)
   end
 
+  def is_meta_wiki?
+    WikiPage.is_meta_wiki?(title)
+  end
+
   def wiki_page_changed?
     saved_change_to_title? || saved_change_to_body? || saved_change_to_is_locked? || saved_change_to_is_deleted? || saved_change_to_other_names?
   end