Bring back Rugged implementation of ListCommitsByOid

This brings back changes in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20432.

For users using Gitaly on top of NFS, accessing the Git data directly
via Rugged may be faster than going through than Gitaly. This merge
request introduces the feature flag `rugged_list_commits_by_oid` to
activate the Rugged method.

For one customer, we saw that ListCommitsByOid was the second highest
used endpoint that may be causing increased load.

1 files changed, 36 insertions, 1 deletions

diff --git a/spec/lib/gitlab/git/commit_spec.rb b/spec/lib/gitlab/git/commit_spec.rb
index 507bf222810..25052a79916 100644
--- a/spec/lib/gitlab/git/commit_spec.rb
+++ b/spec/lib/gitlab/git/commit_spec.rb
@@ -380,7 +380,32 @@ describe Gitlab::Git::Commit, :seed_helper do
       end
     end
 
-    describe '#batch_by_oid' do
+    shared_examples '.batch_by_oid' do
+      context 'with multiple OIDs' do
+        let(:oids) { [SeedRepo::Commit::ID, SeedRepo::FirstCommit::ID] }
+
+        it 'returns multiple commits' do
+          commits = described_class.batch_by_oid(repository, oids)
+
+          expect(commits.count).to eq(2)
+          expect(commits).to all( be_a(Gitlab::Git::Commit) )
+          expect(commits.first.sha).to eq(SeedRepo::Commit::ID)
+          expect(commits.second.sha).to eq(SeedRepo::FirstCommit::ID)
+        end
+      end
+
+      context 'when oids is empty' do
+        it 'returns empty commits' do
+          commits = described_class.batch_by_oid(repository, [])
+
+          expect(commits.count).to eq(0)
+        end
+      end
+    end
+
+    describe '.batch_by_oid with Gitaly enabled' do
+      it_should_behave_like '.batch_by_oid'
+
       context 'when oids is empty' do
         it 'makes no Gitaly request' do
           expect(Gitlab::GitalyClient).not_to receive(:call)
@@ -390,6 +415,16 @@ describe Gitlab::Git::Commit, :seed_helper do
       end
     end
 
+    describe '.batch_by_oid with Rugged enabled', :enable_rugged do
+      it_should_behave_like '.batch_by_oid'
+
+      it 'calls out to the Rugged implementation' do
+        allow_any_instance_of(Rugged).to receive(:rev_parse).with(SeedRepo::Commit::ID).and_call_original
+
+        described_class.batch_by_oid(repository, [SeedRepo::Commit::ID])
+      end
+    end
+
     shared_examples 'extracting commit signature' do
       context 'when the commit is signed' do
         let(:commit_id) { '0b4bc9a49b562e85de7cc9e834518ea6828729b9' }