Restore has_visible_content? to improve performance (cache)

This method was moved to ::Git but it is not cached there which causes performance problems

app/models/repository.rb

@@ -90,6 +90,12 @@ class Repository
     )
   end
+  # we need to have this method here because it is not cached in ::Git and
+  # the method is called multiple times for every request
+  def has_visible_content?
+    branch_count > 0
+  end
+
   def inspect
     "#<#{self.class.name}:#{@disk_path}>"
   end

spec/workers/git_garbage_collect_worker_spec.rb

@@ -31,8 +31,8 @@ describe GitGarbageCollectWorker do
           expect_any_instance_of(Repository).to receive(:after_create_branch).and_call_original
           expect_any_instance_of(Repository).to receive(:branch_names).and_call_original
+          expect_any_instance_of(Repository).to receive(:has_visible_content?).and_call_original
           expect_any_instance_of(Gitlab::Git::Repository).to receive(:branch_count).and_call_original
-          expect_any_instance_of(Gitlab::Git::Repository).to receive(:has_visible_content?).and_call_original
           subject.perform(project.id, :gc, lease_key, lease_uuid)
         end
@@ -77,8 +77,8 @@ describe GitGarbageCollectWorker do
             expect_any_instance_of(Repository).to receive(:after_create_branch).and_call_original
             expect_any_instance_of(Repository).to receive(:branch_names).and_call_original
+            expect_any_instance_of(Repository).to receive(:has_visible_content?).and_call_original
             expect_any_instance_of(Gitlab::Git::Repository).to receive(:branch_count).and_call_original
-            expect_any_instance_of(Gitlab::Git::Repository).to receive(:has_visible_content?).and_call_original
             subject.perform(project.id)
           end