Move EE code out of Chain::Validate::Abilities

This moves EE specific code out of
Gitlab::Ci::Pipeline::Chain::Validate::Abilities and into
EE::Gitlab::Ci::Pipeline::Chain::Validate::Abilities. Since the moved
code was not tested in any way (that I could find at least), some tests
for this were also added.

ee/lib/ee/gitlab/ci/pipeline/chain/validate/abilities.rb

+# frozen_string_literal: true
+
+module EE
+  module Gitlab
+    module Ci
+      module Pipeline
+        module Chain
+          module Validate
+            module Abilities
+              extend ::Gitlab::Utils::Override
+
+              override :perform!
+              def perform!
+                # We check for `builds_enabled?` here so that this error does
+                # not get produced before the "pipelines are disabled" error.
+                if project.builds_enabled? &&
+                    (command.allow_mirror_update && !project.mirror_trigger_builds?)
+                  return error('Pipeline is disabled for mirror updates')
+                end
+
+                super
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

ee/spec/lib/ee/gitlab/ci/pipeline/chain/validate/abilities_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Ci::Pipeline::Chain::Validate::Abilities do
+  set(:project) { create(:project, :repository) }
+  set(:user) { create(:user) }
+
+  let(:pipeline) do
+    build_stubbed(:ci_pipeline, project: project)
+  end
+
+  let(:command) do
+    Gitlab::Ci::Pipeline::Chain::Command
+      .new(project: project, current_user: user, origin_ref: ref)
+  end
+
+  let(:step) { described_class.new(pipeline, command) }
+  let(:ref) { 'master' }
+
+  describe '#perform!' do
+    context 'when triggering builds for project mirrors is disabled' do
+      it 'returns an error' do
+        project.add_developer(user)
+
+        allow(command)
+          .to receive(:allow_mirror_update)
+          .and_return(true)
+
+        allow(project)
+          .to receive(:mirror_trigger_builds?)
+          .and_return(false)
+
+        step.perform!
+
+        expect(pipeline.errors.to_a)
+          .to include('Pipeline is disabled for mirror updates')
+      end
+    end
+  end
+end

lib/gitlab/ci/pipeline/chain/validate/abilities.rb

@@ -14,10 +14,6 @@ module Gitlab
                 return error('Pipelines are disabled!')
               end
 
-              if @command.allow_mirror_update && !project.mirror_trigger_builds?
-                return error('Pipeline is disabled for mirror updates')
-              end
-
               unless allowed_to_trigger_pipeline?
                 if can?(current_user, :create_pipeline, project)
                   return error("Insufficient permissions for protected ref '#{command.ref}'")
@@ -58,3 +54,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::Ci::Pipeline::Chain::Validate::Abilities.prepend(EE::Gitlab::Ci::Pipeline::Chain::Validate::Abilities)