Cache various Repository Git operations

This caches the output of the following methods:

* Repository#empty?
* Repository#has_visible_content?
* Repository#root_ref

The cache for Repository#has_visible_content? is flushed whenever a
commit is pushed to a new branch or an existing branch is removed.
The cache for Repository#root_ref is only flushed whenever a user
changes the default branch of a project. The cache for Repository#empty?
is never explicitly flushed as there's no need for it.

2 files changed, 114 insertions, 3 deletions

diff --git a/spec/models/repository_spec.rb b/spec/models/repository_spec.rb
index c484ae8fc8c..753012be578 100644
--- a/spec/models/repository_spec.rb
+++ b/spec/models/repository_spec.rb
@@ -232,11 +232,92 @@ describe Repository, models: true do
     end
 
     describe 'when there are branches' do
-      before do
-        allow(repository.raw_repository).to receive(:branch_count).and_return(3)
+      it 'returns true' do
+        expect(repository.raw_repository).to receive(:branch_count).and_return(3)
+
+        expect(subject).to eq(true)
+      end
+
+      it 'caches the output' do
+        expect(repository.raw_repository).to receive(:branch_count).
+          once.
+          and_return(3)
+
+        repository.has_visible_content?
+        repository.has_visible_content?
       end
+    end
+  end
+
+  describe '#empty?' do
+    let(:empty_repository) { create(:project_empty_repo).repository }
+
+    it 'returns true for an empty repository' do
+      expect(empty_repository.empty?).to eq(true)
+    end
+
+    it 'returns false for a non-empty repository' do
+      expect(repository.empty?).to eq(false)
+    end
+
+    it 'caches the output' do
+      expect(repository.raw_repository).to receive(:empty?).
+        once.
+        and_return(false)
+
+      repository.empty?
+      repository.empty?
+    end
+  end
+
+  describe '#root_ref' do
+    it 'returns a branch name' do
+      expect(repository.root_ref).to be_an_instance_of(String)
+    end
+
+    it 'caches the output' do
+      expect(repository.raw_repository).to receive(:root_ref).
+        once.
+        and_return('master')
+
+      repository.root_ref
+      repository.root_ref
+    end
+  end
+
+  describe '#expire_cache' do
+    it 'expires all caches' do
+      expect(repository).to receive(:expire_branch_cache)
+
+      repository.expire_cache
+    end
+  end
+
+  describe '#expire_root_ref_cache' do
+    it 'expires the root reference cache' do
+      repository.root_ref
+
+      expect(repository.raw_repository).to receive(:root_ref).
+        once.
+        and_return('foo')
+
+      repository.expire_root_ref_cache
+
+      expect(repository.root_ref).to eq('foo')
+    end
+  end
+
+  describe '#expire_has_visible_content_cache' do
+    it 'expires the visible content cache' do
+      repository.has_visible_content?
+
+      expect(repository.raw_repository).to receive(:branch_count).
+        once.
+        and_return(0)
+
+      repository.expire_has_visible_content_cache
 
-      it { is_expected.to eq(true) }
+      expect(repository.has_visible_content?).to eq(false)
     end
   end
 end
diff --git a/spec/services/git_push_service_spec.rb b/spec/services/git_push_service_spec.rb
index c1080ef190a..349809743c7 100644
--- a/spec/services/git_push_service_spec.rb
+++ b/spec/services/git_push_service_spec.rb
@@ -21,6 +21,18 @@ describe GitPushService, services: true do
       end
 
       it { is_expected.to be_truthy }
+
+      it 'flushes general cached data' do
+        expect(project.repository).to receive(:expire_cache)
+
+        subject
+      end
+
+      it 'flushes the visible content cache' do
+        expect(project.repository).to receive(:expire_has_visible_content_cache)
+
+        subject
+      end
     end
 
     context 'existing branch' do
@@ -29,6 +41,12 @@ describe GitPushService, services: true do
       end
 
       it { is_expected.to be_truthy }
+
+      it 'flushes general cached data' do
+        expect(project.repository).to receive(:expire_cache)
+
+        subject
+      end
     end
 
     context 'rm branch' do
@@ -37,6 +55,18 @@ describe GitPushService, services: true do
       end
 
       it { is_expected.to be_truthy }
+
+      it 'flushes the visible content cache' do
+        expect(project.repository).to receive(:expire_has_visible_content_cache)
+
+        subject
+      end
+
+      it 'flushes general cached data' do
+        expect(project.repository).to receive(:expire_cache)
+
+        subject
+      end
     end
   end