Fix Ci::Pipeline#all_merge_requests missing forked MRs

Ci::Pipeline#all_merge_requests was only returning merge requests
for that project, but it should include merge requests from forks
as well.
Signed-off-by: Rémy Coutable <remy@rymai.me>

app/models/ci/pipeline.rb

@@ -652,9 +652,9 @@ module Ci
     def all_merge_requests
       @all_merge_requests ||=
         if merge_request?
-          project.merge_requests.where(id: merge_request_id)
+          MergeRequest.where(id: merge_request_id)
         else
-          project.merge_requests.where(source_branch: ref)
+          MergeRequest.where(source_project_id: project_id, source_branch: ref)
         end
     end
 

spec/models/ci/pipeline_spec.rb

 require 'spec_helper'
 
 describe Ci::Pipeline, :mailer do
+  include ProjectForksHelper
+
   let(:user) { create(:user) }
   set(:project) { create(:project) }
 
@@ -2114,16 +2116,18 @@ describe Ci::Pipeline, :mailer do
 
   describe "#all_merge_requests" do
     let(:project) { create(:project) }
-    let(:pipeline) { create(:ci_empty_pipeline, status: 'created', project: project, ref: 'master') }
+
+    shared_examples 'a method that returns all merge requests for a given pipeline' do
+      let(:pipeline) { create(:ci_empty_pipeline, status: 'created', project: pipeline_project, ref: 'master') }
 
       it "returns all merge requests having the same source branch" do
-      merge_request = create(:merge_request, source_project: project, source_branch: pipeline.ref)
+        merge_request = create(:merge_request, source_project: pipeline_project, target_project: project, source_branch: pipeline.ref)
 
         expect(pipeline.all_merge_requests).to eq([merge_request])
       end
 
       it "doesn't return merge requests having a different source branch" do
-      create(:merge_request, source_project: project, source_branch: 'feature', target_branch: 'master')
+        create(:merge_request, source_project: pipeline_project, target_project: project, source_branch: 'feature', target_branch: 'master')
 
         expect(pipeline.all_merge_requests).to be_empty
       end
@@ -2135,14 +2139,14 @@ describe Ci::Pipeline, :mailer do
         let!(:pipeline) do
           create(:ci_pipeline,
                  source: :merge_request,
-               project: project,
+                 project: pipeline_project,
                  ref: source_branch,
                  merge_request: merge_request)
         end
 
         let(:merge_request) do
           create(:merge_request,
-               source_project: project,
+                 source_project: pipeline_project,
                  source_branch: source_branch,
                  target_project: project,
                  target_branch: target_branch)
@@ -2158,14 +2162,14 @@ describe Ci::Pipeline, :mailer do
           let!(:pipeline_2) do
             create(:ci_pipeline,
                    source: :merge_request,
-                 project: project,
+                   project: pipeline_project,
                    ref: source_branch,
                    merge_request: merge_request_2)
           end
 
           let(:merge_request_2) do
             create(:merge_request,
-                 source_project: project,
+                   source_project: pipeline_project,
                    source_branch: source_branch,
                    target_project: project,
                    target_branch: target_branch_2)
@@ -2178,6 +2182,19 @@ describe Ci::Pipeline, :mailer do
       end
     end
 
+    it_behaves_like 'a method that returns all merge requests for a given pipeline' do
+      let(:pipeline_project) { project }
+    end
+
+    context 'for a fork' do
+      let(:fork) { fork_project(project) }
+
+      it_behaves_like 'a method that returns all merge requests for a given pipeline' do
+        let(:pipeline_project) { fork }
+      end
+    end
+  end
+
   describe '#stuck?' do
     before do
       create(:ci_build, :pending, pipeline: pipeline)