Move the `ancestors_upto` to `Project` and `Namespace`

app/models/concerns/group_descendant.rb

 module GroupDescendant
+  # Returns the hierarchy of a project or group in the from of a hash upto a
+  # given top.
+  #
+  # > project.hierarchy
+  # => { parent_group => { child_group => project } }
   def hierarchy(hierarchy_top = nil, preloaded = nil)
     preloaded ||= ancestors_upto(hierarchy_top)
     expand_hierarchy_for_child(self, self, hierarchy_top, preloaded)
   end
+  # Merges all hierarchies of the given groups or projects into an array of
+  # hashes. All ancestors need to be loaded into the given `descendants` to avoid
+  # queries down the line.
+  #
+  # > GroupDescendant.merge_hierarchy([project, child_group, child_group2, parent])
+  # => { parent => [{ child_group => project}, child_group2] }
   def self.build_hierarchy(descendants, hierarchy_top = nil)
     descendants = Array.wrap(descendants).uniq
     return [] if descendants.empty?
@@ -21,16 +32,6 @@ module GroupDescendant
   private
-  def ancestors_upto(hierarchy_top = nil)
-    if self.is_a?(Group)
-      Gitlab::GroupHierarchy.new(Group.where(id: id))
-        .ancestors(upto: hierarchy_top)
-    else
-      Gitlab::GroupHierarchy.new(Group.where(id: parent_id))
-        .base_and_ancestors(upto: hierarchy_top)
-    end
-  end
-
   def expand_hierarchy_for_child(child, hierarchy, hierarchy_top, preloaded)
     parent = hierarchy_top if hierarchy_top && child.parent_id == hierarchy_top.id
     parent ||= preloaded.detect { |possible_parent| possible_parent.is_a?(Group) && possible_parent.id == child.parent_id }

app/models/namespace.rb

@@ -160,6 +160,13 @@ class Namespace < ActiveRecord::Base
       .base_and_ancestors
   end
+  # returns all ancestors upto but excluding the the given namespace
+  # when no namespace is given, all ancestors upto the top are returned
+  def ancestors_upto(top = nil)
+    Gitlab::GroupHierarchy.new(self.class.where(id: id))
+      .ancestors(upto: top)
+  end
+
   def self_and_ancestors
     return self.class.where(id: id) unless parent_id

app/models/project.rb

@@ -471,6 +471,13 @@ class Project < ActiveRecord::Base
     end
   end
+  # returns all ancestor-groups upto but excluding the given namespace
+  # when no namespace is given, all ancestors upto the top are returned
+  def ancestors_upto(top = nil)
+    Gitlab::GroupHierarchy.new(Group.where(id: namespace_id))
+      .base_and_ancestors(upto: top)
+  end
+
   def lfs_enabled?
     return namespace.lfs_enabled? if self[:lfs_enabled].nil?

spec/models/namespace_spec.rb

@@ -151,6 +151,20 @@ describe Namespace do
     end
   end
+  describe '#ancestors_upto', :nested_groups do
+    let(:parent) { create(:group) }
+    let(:child) { create(:group, parent: parent) }
+    let(:child2) { create(:group, parent: child) }
+
+    it 'returns all ancestors when no namespace is given' do
+      expect(child2.ancestors_upto).to contain_exactly(child, parent)
+    end
+
+    it 'includes ancestors upto but excluding the given ancestor' do
+      expect(child2.ancestors_upto(parent)).to contain_exactly(child)
+    end
+  end
+
   describe '#move_dir' do
     before do
       @namespace = create :namespace

spec/models/project_spec.rb

@@ -1731,6 +1731,21 @@ describe Project do
     it { expect(project.gitea_import?).to be true }
   end
+  describe '#ancestors_upto', :nested_groups do
+    let(:parent) { create(:group) }
+    let(:child) { create(:group, parent: parent) }
+    let(:child2) { create(:group, parent: child) }
+    let(:project) { create(:project, namespace: child2) }
+
+    it 'returns all ancestors when no namespace is given' do
+      expect(project.ancestors_upto).to contain_exactly(child2, child, parent)
+    end
+
+    it 'includes ancestors upto but excluding the given ancestor' do
+      expect(project.ancestors_upto(parent)).to contain_exactly(child2, child)
+    end
+  end
+
   describe '#lfs_enabled?' do
     let(:project) { create(:project) }