Flush repository cache before import project data

GitHub Pull Requests importer handle with the repository while
importing data, we need to make sure that the cached values are valid.

app/models/repository.rb

@@ -364,6 +364,11 @@ class Repository
     expire_tag_count_cache
   end
 
+  def before_import
+    expire_emptiness_caches
+    expire_exists_cache
+  end
+
   # Runs code after a repository has been forked/imported.
   def after_import
     expire_emptiness_caches

app/services/projects/import_service.rb

@@ -46,6 +46,8 @@ module Projects
     def import_data
       return unless has_importer?
 
+      project.repository.before_import
+
       unless importer.execute
         raise Error, 'The remote data could not be imported.'
       end

spec/models/repository_spec.rb

@@ -612,6 +612,20 @@ describe Repository, models: true do
     end
   end
 
+  describe '#before_import' do
+    it 'flushes the emptiness cachess' do
+      expect(repository).to receive(:expire_emptiness_caches)
+
+      repository.before_import
+    end
+
+    it 'flushes the exists cache' do
+      expect(repository).to receive(:expire_exists_cache)
+
+      repository.before_import
+    end
+  end
+
   describe '#after_import' do
     it 'flushes the emptiness cachess' do
       expect(repository).to receive(:expire_emptiness_caches)

spec/services/projects/import_service_spec.rb

@@ -72,6 +72,23 @@ describe Projects::ImportService, services: true do
         expect(result[:status]).to eq :success
       end
 
+      it 'flushes various caches' do
+        expect_any_instance_of(Gitlab::Shell).to receive(:import_repository).
+          with(project.path_with_namespace, project.import_url).
+          and_return(true)
+
+        expect_any_instance_of(Gitlab::GithubImport::Importer).to receive(:execute).
+          and_return(true)
+
+        expect_any_instance_of(Repository).to receive(:expire_emptiness_caches).
+          and_call_original
+
+        expect_any_instance_of(Repository).to receive(:expire_exists_cache).
+          and_call_original
+
+        subject.execute
+      end
+
       it 'fails if importer fails' do
         expect_any_instance_of(Gitlab::Shell).to receive(:import_repository).with(project.path_with_namespace, project.import_url).and_return(true)
         expect_any_instance_of(Gitlab::GithubImport::Importer).to receive(:execute).and_return(false)