Forks get default_git_depth 0 if the origin is nil

If the origin project has no default_git_depth set (i.e. nil) set the
fork's default_git_depth to 0

app/models/project_ci_cd_setting.rb

@@ -8,7 +8,7 @@ class ProjectCiCdSetting < ApplicationRecord
   DEFAULT_GIT_DEPTH = 50
-  before_create :set_default_git_depth, unless: :default_git_depth?
+  before_create :set_default_git_depth
   validates :default_git_depth,
     numericality: {
@@ -31,6 +31,8 @@ class ProjectCiCdSetting < ApplicationRecord
   private
   def set_default_git_depth
+    return if default_git_depth
+
     self.default_git_depth = DEFAULT_GIT_DEPTH
   end
 end

app/services/projects/fork_service.rb

@@ -43,7 +43,7 @@ module Projects
         shared_runners_enabled:    @project.shared_runners_enabled,
         namespace_id:              target_namespace.id,
         fork_network:              fork_network,
-        ci_cd_settings_attributes: { default_git_depth: @project.default_git_depth },
+        ci_cd_settings_attributes: { default_git_depth: @project.default_git_depth || 0 },
         # We need to assign the fork network membership after the project has
         # been instantiated to avoid ActiveRecord trying to create it when
         # initializing the project, as that would cause a foreign key constraint
@@ -57,10 +57,7 @@ module Projects
       new_params.merge!(@project.object_pool_params)
-      new_project = CreateService.new(current_user, new_params).execute do |p|
-        p.build_ci_cd_settings(default_git_depth: @project.default_git_depth)
-      end
-
+      new_project = CreateService.new(current_user, new_params).execute
       return new_project unless new_project.persisted?
       # Set the forked_from_project relation after saving to avoid having to

spec/models/project_ci_cd_setting_spec.rb

@@ -37,10 +37,10 @@ describe ProjectCiCdSetting do
     it 'does not set default value if present' do
       project = build(:project)
-      project.build_ci_cd_settings(default_git_depth: 42)
+      project.build_ci_cd_settings(default_git_depth: 0)
       project.save!
-      expect(project.reload.ci_cd_settings.default_git_depth).to eq(42)
+      expect(project.reload.ci_cd_settings.default_git_depth).to eq(0)
     end
   end
 end

spec/services/projects/fork_service_spec.rb

@@ -146,10 +146,26 @@ describe Projects::ForkService do
       end
       context "CI/CD settings" do
-        it "inherits default_git_depth from the origin project" do
-          @from_project.update(default_git_depth: 42)
-          @to_project = fork_project(@from_project, @to_user)
-          expect(@to_project.default_git_depth).to eq(42)
+        let(:to_project) { fork_project(@from_project, @to_user) }
+
+        context "when origin has git depth specified" do
+          before do
+            @from_project.update(default_git_depth: 42)
+          end
+
+          it "inherits default_git_depth from the origin project" do
+            expect(to_project.default_git_depth).to eq(42)
+          end
+        end
+
+        context "when origin does not define git depth" do
+          before do
+            @from_project.update!(default_git_depth: nil)
+          end
+
+          it "the fork has git depth set to 0" do
+            expect(to_project.default_git_depth).to eq(0)
+          end
         end
       end