Merge branch 'fix/private-references' into 'master'

Show referenced MRs & Issues only when the current viewer can access them

This addresses both issues identified in #6066.

## The private MR by user `remy2` with a note referencing to a public issue

![Screen_Shot_2016-01-12_at_16.45.02](/uploads/c245ec2c1fdea1f9ba05183c24e142d9/Screen_Shot_2016-01-12_at_16.45.02.png)

---

## The public issue viewed by user `remy` **who doesn't have access to `remy2/private-project`** before the fix

![Screen_Shot_2016-01-12_at_18.14.50](/uploads/8db5580e803f5bddd6cb935233c579a0/Screen_Shot_2016-01-12_at_18.14.50.png)

---

## The public issue viewed by user `remy` **who doesn't have access to `remy2/private-project`** with the fix

![Screen_Shot_2016-01-13_at_12.02.32](/uploads/cb199f7b78191fba486a11412412e307/Screen_Shot_2016-01-13_at_12.02.32.png)

---

## The public issue viewed by user `remy2` with the fix (no change)

![Screen_Shot_2016-01-13_at_11.54.06](/uploads/ddece590d69f597a95559beddcd36660/Screen_Shot_2016-01-13_at_11.54.06.png)


See merge request !2405

1 files changed, 24 insertions, 0 deletions

diff --git a/spec/models/note_spec.rb b/spec/models/note_spec.rb
index 151a29e974b..9182b42661d 100644
--- a/spec/models/note_spec.rb
+++ b/spec/models/note_spec.rb
@@ -178,6 +178,30 @@ describe Note, models: true do
     end
   end
 
+  describe "cross_reference_not_visible_for?" do
+    let(:private_user)    { create(:user) }
+    let(:private_project) { create(:project, namespace: private_user.namespace).tap { |p| p.team << [private_user, :master] } }
+    let(:private_issue)   { create(:issue, project: private_project) }
+
+    let(:ext_proj)  { create(:project, :public) }
+    let(:ext_issue) { create(:issue, project: ext_proj) }
+
+    let(:note) do
+      create :note,
+        noteable: ext_issue, project: ext_proj,
+        note: "mentioned in issue #{private_issue.to_reference(ext_proj)}",
+        system: true
+    end
+
+    it "returns true" do
+      expect(note.cross_reference_not_visible_for?(ext_issue.author)).to be_truthy
+    end
+
+    it "returns false" do
+      expect(note.cross_reference_not_visible_for?(private_user)).to be_falsy
+    end
+  end
+
   describe "set_award!" do
     let(:issue) { create :issue }