Merge branch 'bug/git_hooks' into 'master'

Fix fast-forward merge requests git hooks validations

Current implementations checks git hooks during merge request action issued by Web UI to prevent a git merge action failing and not reporting back to the UI (introduced by !326).
The problem is that we shouldn't make the check the merge commit when we are using a Fast Forward merge type.

Fixes gitlab-org/gitlab-ee#598

See merge request !427

app/services/merge_requests/merge_service.rb

@@ -9,7 +9,7 @@ module MergeRequests
     attr_reader :merge_request
 
     def execute(merge_request)
-      if @project.merge_requests_ff_only_enabled && !self.is_a?(FfMergeService)
+      if project.merge_requests_ff_only_enabled && !self.is_a?(FfMergeService)
         FfMergeService.new(project, current_user, params).execute(merge_request)
         return
       end
@@ -29,6 +29,8 @@ module MergeRequests
     end
 
     def hooks_validation_pass?(merge_request)
+      return true if project.merge_requests_ff_only_enabled
+
       git_hook = merge_request.project.git_hook
       return true unless git_hook
 

spec/services/merge_requests/merge_service_spec.rb

@@ -96,5 +96,13 @@ describe MergeRequests::MergeService, services: true do
         expect(merge_request.merge_error).not_to be_empty
       end
     end
+
+    context 'fast forward merge request' do
+      it 'returns true when fast forward is enabled' do
+        allow(project).to receive(:merge_requests_ff_only_enabled) { true }
+
+        expect(service.hooks_validation_pass?(merge_request)).to be_truthy
+      end
+    end
   end
 end