Change forks method to has_many relation

app/models/project.rb

@@ -97,9 +97,12 @@ class Project < ActiveRecord::Base
   has_one :gitlab_issue_tracker_service, dependent: :destroy
   has_one :external_wiki_service, dependent: :destroy
 
-  has_one :forked_project_link, dependent: :destroy, foreign_key: "forked_to_project_id"
+  has_one  :forked_project_link,  dependent: :destroy, foreign_key: "forked_to_project_id"
+  has_one  :forked_from_project,  through:   :forked_project_link
+
+  has_many :forked_project_links, foreign_key: "forked_from_project_id"
+  has_many :forks,                through:     :forked_project_links, source: :forked_to_project
 
-  has_one :forked_from_project, through: :forked_project_link
   # Merge Requests for target project should be removed with it
   has_many :merge_requests,     dependent: :destroy, foreign_key: 'target_project_id'
   # Merge requests from source project should be kept when source project was removed
@@ -734,10 +737,6 @@ class Project < ActiveRecord::Base
     forks.count
   end
 
-  def forks
-    ForkedProjectLink.where(forked_from_project_id: self.id)
-  end
-
   def find_label(name)
     labels.find_by(name: name)
   end

app/services/projects/update_service.rb

@@ -44,8 +44,7 @@ module Projects
     end
 
     def update_forks_visibility_level(new_level)
-      project.forks.each do |forked_link|
-        forked_project = forked_link.forked_to_project
+      project.forks.each do |forked_project|
         fork_level = forked_project.visibility_level
 
         if fork_level > new_level.to_i