Remove feature gate for ListNewCommits

Introduced by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20087,
this has been tested on .com now, and is stable.

Closes https://gitlab.com/gitlab-org/gitaly/issues/1286
Closes https://gitlab.com/gitlab-org/gitaly/issues/1233

lib/gitlab/git/repository.rb

@@ -366,18 +366,9 @@ module Gitlab
         end
       end
 
-      # Gitaly migration: https://gitlab.com/gitlab-org/gitaly/issues/1233
       def new_commits(newrev)
-        gitaly_migrate(:new_commits) do |is_enabled|
-          if is_enabled
-            gitaly_ref_client.list_new_commits(newrev)
-          else
-            refs = Gitlab::GitalyClient::StorageSettings.allow_disk_access do
-              rev_list(including: newrev, excluding: :all).split("\n").map(&:strip)
-            end
-
-            Gitlab::Git::Commit.batch_by_oid(self, refs)
-          end
+        wrapped_gitaly_errors do
+          gitaly_ref_client.list_new_commits(newrev)
         end
       end
 

spec/models/repository_spec.rb

@@ -296,41 +296,31 @@ describe Repository do
   end
 
   describe '#new_commits' do
-    shared_examples 'finding unreferenced commits' do
-      set(:project) { create(:project, :repository) }
-      let(:repository) { project.repository }
+    set(:project) { create(:project, :repository) }
+    let(:repository) { project.repository }
 
-      subject { repository.new_commits(rev) }
+    subject { repository.new_commits(rev) }
 
-      context 'when there are no new commits' do
-        let(:rev) { repository.commit.id }
+    context 'when there are no new commits' do
+      let(:rev) { repository.commit.id }
 
-        it 'returns an empty array' do
-          expect(subject).to eq([])
-        end
+      it 'returns an empty array' do
+        expect(subject).to eq([])
       end
+    end
 
-      context 'when new commits are found' do
-        let(:branch) { 'orphaned-branch' }
-        let!(:rev) { repository.commit(branch).id }
+    context 'when new commits are found' do
+      let(:branch) { 'orphaned-branch' }
+      let!(:rev) { repository.commit(branch).id }
 
-        it 'returns the commits' do
-          repository.delete_branch(branch)
+      it 'returns the commits' do
+        repository.delete_branch(branch)
 
-          expect(subject).not_to be_empty
-          expect(subject).to all( be_a(::Commit) )
-          expect(subject.size).to eq(1)
-        end
+        expect(subject).not_to be_empty
+        expect(subject).to all( be_a(::Commit) )
+        expect(subject.size).to eq(1)
       end
     end
-
-    context 'when Gitaly handles the request' do
-      it_behaves_like 'finding unreferenced commits'
-    end
-
-    context 'when Gitaly is disabled', :disable_gitaly do
-      it_behaves_like 'finding unreferenced commits'
-    end
   end
 
   describe '#commits_by' do