Exclude system notes from Project.trending

Having many system notes isn't really an indication of a project being
trending. Including these notes would lead to projects with lots of
commit cross references (for example) showing up in the trending
projects list.

app/models/project.rb

@@ -380,6 +380,7 @@ class Project < ActiveRecord::Base
         SELECT project_id, COUNT(*) AS amount
         FROM notes
         WHERE created_at >= #{sanitize(since)}
+        AND system IS FALSE
         GROUP BY project_id
       ) join_note_counts ON projects.id = join_note_counts.project_id"
 

spec/models/project_spec.rb

@@ -826,6 +826,14 @@ describe Project, models: true do
         expect(subject).to eq([project2, project1])
       end
     end
+
+    it 'does not take system notes into account' do
+      10.times do
+        create(:note_on_commit, project: project2, system: true)
+      end
+
+      expect(described_class.trending.to_a).to eq([project1, project2])
+    end
   end
 
   describe '.visible_to_user' do