Exclude status itself from context query (#7083)

ancestor_statuses and descendant_statuses used to include the root status
itself, but the behavior is confusing because the root status is not
an ancestor nor descendant.

app/models/concerns/status_threading_concern.rb

@@ -15,16 +15,12 @@ module StatusThreadingConcern
 
   def ancestor_ids
     Rails.cache.fetch("ancestors:#{id}") do
-      ancestors_without_self.pluck(:id)
+      ancestor_statuses.pluck(:id)
     end
   end
 
-  def ancestors_without_self
-    ancestor_statuses - [self]
-  end
-
   def ancestor_statuses
-    Status.find_by_sql([<<-SQL.squish, id: id])
+    Status.find_by_sql([<<-SQL.squish, id: in_reply_to_id])
       WITH RECURSIVE search_tree(id, in_reply_to_id, path)
       AS (
         SELECT id, in_reply_to_id, ARRAY[id]
@@ -43,11 +39,7 @@ module StatusThreadingConcern
   end
 
   def descendant_ids
-    descendants_without_self.pluck(:id)
-  end
-
-  def descendants_without_self
-    descendant_statuses - [self]
+    descendant_statuses.pluck(:id)
   end
 
   def descendant_statuses
@@ -56,7 +48,7 @@ module StatusThreadingConcern
       AS (
         SELECT id, ARRAY[id]
         FROM statuses
-        WHERE id = :id
+        WHERE in_reply_to_id = :id
         UNION ALL
         SELECT statuses.id, path || statuses.id
         FROM search_tree