Cache commits on the repository model

Now, when requesting a commit from the Repository model, the results are
not cached. This means we're fetching the same commit by oid multiple times
during the same request. To prevent us from doing this, we now cache
results. Caching is done only based on object id (aka SHA).

Given we cache on the Repository model, results are scoped to the
associated project, eventhough the change of two repositories having the
same oids for different commits is small.

3 files changed, 23 insertions, 3 deletions

diff --git a/spec/controllers/projects/pipelines_controller_spec.rb b/spec/controllers/projects/pipelines_controller_spec.rb
index f1ad5dd84ff..1604a2da485 100644
--- a/spec/controllers/projects/pipelines_controller_spec.rb
+++ b/spec/controllers/projects/pipelines_controller_spec.rb
@@ -46,7 +46,7 @@ describe Projects::PipelinesController do
 
     context 'when performing gitaly calls', :request_store do
       it 'limits the Gitaly requests' do
-        expect { subject }.to change { Gitlab::GitalyClient.get_request_count }.by(10)
+        expect { subject }.to change { Gitlab::GitalyClient.get_request_count }.by(8)
       end
     end
   end
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 73e038b61ed..2b8aa7cf9c3 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -86,7 +86,7 @@ describe MergeRequest do
 
     context 'when the target branch does not exist' do
       before do
-        project.repository.raw_repository.delete_branch(subject.target_branch)
+        project.repository.rm_branch(subject.author, subject.target_branch)
       end
 
       it 'returns nil' do
@@ -1388,7 +1388,7 @@ describe MergeRequest do
 
     context 'when the target branch does not exist' do
       before do
-        subject.project.repository.raw_repository.delete_branch(subject.target_branch)
+        subject.project.repository.rm_branch(subject.author, subject.target_branch)
       end
 
       it 'returns nil' do
diff --git a/spec/models/repository_spec.rb b/spec/models/repository_spec.rb
index 39d188f18af..aa376d46a67 100644
--- a/spec/models/repository_spec.rb
+++ b/spec/models/repository_spec.rb
@@ -2238,4 +2238,24 @@ describe Repository do
       end
     end
   end
+
+  describe 'commit cache' do
+    set(:project) { create(:project, :repository) }
+
+    it 'caches based on SHA' do
+      # Gets the commit oid, and warms the cache
+      oid = project.commit.id
+
+      expect(Gitlab::Git::Commit).not_to receive(:find).once
+
+      project.commit_by(oid: oid)
+    end
+
+    it 'caches nil values' do
+      expect(Gitlab::Git::Commit).to receive(:find).once
+
+      project.commit_by(oid: '1' * 40)
+      project.commit_by(oid: '1' * 40)
+    end
+  end
 end