Find forks within users/namespaces using fork memberships

app/models/fork_network.rb

@@ -8,4 +8,8 @@ class ForkNetwork < ActiveRecord::Base
   def add_root_as_member
     projects << root_project
   end
+
+  def find_forks_in(other_projects)
+    projects.where(id: other_projects)
+  end
 end

app/models/namespace.rb

@@ -139,7 +139,9 @@ class Namespace < ActiveRecord::Base
   end
   def find_fork_of(project)
-    projects.joins(:forked_project_link).find_by('forked_project_links.forked_from_project_id = ?', project.id)
+    return nil unless project.fork_network
+
+    project.fork_network.find_forks_in(projects).first
   end
   def lfs_enabled?

app/models/project.rb

@@ -1009,6 +1009,11 @@ class Project < ActiveRecord::Base
   end
   def forked?
+    return true if fork_network && fork_network.root_project != self
+
+    # TODO: Use only the above conditional using the `fork_network`
+    # This is the old conditional that looks at the `forked_project_link`, we
+    # fall back to this while we're migrating the new models
     !(forked_project_link.nil? || forked_project_link.forked_from_project.nil?)
   end

app/models/user.rb

@@ -697,15 +697,7 @@ class User < ActiveRecord::Base
   end
   def fork_of(project)
-    links = ForkedProjectLink.where(
-      forked_from_project_id: project,
-      forked_to_project_id: personal_projects.unscope(:order)
-    )
-    if links.any?
-      links.first.forked_to_project
-    else
-      nil
-    end
+    namespace.find_fork_of(project)
   end
   def ldap_user?

spec/factories/fork_networks.rb

+FactoryGirl.define do
+  factory :fork_network do
+    association :root_project, factory: :project
+  end
+end

spec/models/fork_network_spec.rb

@@ -12,6 +12,18 @@ describe ForkNetwork do
     end
   end
+  describe '#find_fork_in' do
+    it 'finds all fork of the current network in al collection' do
+      network = create(:fork_network)
+      root_project = network.root_project
+      another_project = fork_project(root_project)
+      create(:project)
+
+      expect(network.find_forks_in(Project.all))
+               .to contain_exactly(another_project, root_project)
+    end
+  end
+
   context 'for a deleted project' do
     it 'keeps the fork network' do
       project = create(:project, :public)

spec/models/namespace_spec.rb

 require 'spec_helper'
 describe Namespace do
+  include ProjectForksHelper
+
   let!(:namespace) { create(:namespace) }
   describe 'associations' do
@@ -520,4 +522,25 @@ describe Namespace do
       end
     end
   end
+
+  describe '#has_forks_of?' do
+    let(:project) { create(:project, :public) }
+    let!(:forked_project) { fork_project(project, namespace.owner, namespace: namespace) }
+
+    before do
+      # Reset the fork network relation
+      project.reload
+    end
+
+    it 'knows if there is a direct fork in the namespace' do
+      expect(namespace.find_fork_of(project)).to eq(forked_project)
+    end
+
+    it 'knows when there is as fork-of-fork in the namespace' do
+      other_namespace = create(:namespace)
+      other_fork = fork_project(forked_project, other_namespace.owner, namespace: other_namespace)
+
+      expect(other_namespace.find_fork_of(project)).to eq(other_fork)
+    end
+  end
 end

spec/models/user_spec.rb

@@ -1456,6 +1456,23 @@ describe User do
     end
   end
+  describe '#fork_of' do
+    let(:user) { create(:user) }
+
+    it "returns a user's fork of a project" do
+      project = create(:project, :public)
+      user_fork = fork_project(project, user, namespace: user.namespace)
+
+      expect(user.fork_of(project)).to eq(user_fork)
+    end
+
+    it 'returns nil if the project does not have a fork network' do
+      project = create(:project)
+
+      expect(user.fork_of(project)).to be_nil
+    end
+  end
+
   describe '#can_be_removed?' do
     subject { create(:user) }