New feature flag for Gitaly service

Feature flag to change between old ruby and new go implementations
of Gitaly gRPC call to FilterShasWithSignatures.

Part of https://gitlab.com/gitlab-org/gitaly/issues/2157

lib/feature/gitaly.rb

@@ -10,6 +10,7 @@ class Feature
         inforef_uploadpack_cache
         get_all_lfs_pointers_go
         get_tag_messages_go
+        filter_shas_with_signatures_go
       ].freeze
 
     DEFAULT_ON_FLAGS = Set.new([]).freeze

spec/requests/api/internal/base_spec.rb

@@ -326,7 +326,7 @@ describe API::Internal::Base do
           expect(json_response["gitaly"]["repository"]["relative_path"]).to eq(project.repository.gitaly_repository.relative_path)
           expect(json_response["gitaly"]["address"]).to eq(Gitlab::GitalyClient.address(project.repository_storage))
           expect(json_response["gitaly"]["token"]).to eq(Gitlab::GitalyClient.token(project.repository_storage))
-          expect(json_response["gitaly"]["features"]).to eq('gitaly-feature-get-all-lfs-pointers-go' => 'true', 'gitaly-feature-inforef-uploadpack-cache' => 'true', 'gitaly-feature-get-tag-messages-go' => 'true')
+          expect(json_response["gitaly"]["features"]).to eq('gitaly-feature-get-all-lfs-pointers-go' => 'true', 'gitaly-feature-inforef-uploadpack-cache' => 'true', 'gitaly-feature-get-tag-messages-go' => 'true', 'gitaly-feature-filter-shas-with-signatures-go' => 'true')
           expect(user.reload.last_activity_on).to eql(Date.today)
         end
       end
@@ -346,7 +346,7 @@ describe API::Internal::Base do
             expect(json_response["gitaly"]["repository"]["relative_path"]).to eq(project.repository.gitaly_repository.relative_path)
             expect(json_response["gitaly"]["address"]).to eq(Gitlab::GitalyClient.address(project.repository_storage))
             expect(json_response["gitaly"]["token"]).to eq(Gitlab::GitalyClient.token(project.repository_storage))
-            expect(json_response["gitaly"]["features"]).to eq('gitaly-feature-get-all-lfs-pointers-go' => 'true', 'gitaly-feature-inforef-uploadpack-cache' => 'true', 'gitaly-feature-get-tag-messages-go' => 'true')
+            expect(json_response["gitaly"]["features"]).to eq('gitaly-feature-get-all-lfs-pointers-go' => 'true', 'gitaly-feature-inforef-uploadpack-cache' => 'true', 'gitaly-feature-get-tag-messages-go' => 'true', 'gitaly-feature-filter-shas-with-signatures-go' => 'true')
             expect(user.reload.last_activity_on).to be_nil
           end
         end
@@ -588,7 +588,7 @@ describe API::Internal::Base do
           expect(json_response["gitaly"]["repository"]["relative_path"]).to eq(project.repository.gitaly_repository.relative_path)
           expect(json_response["gitaly"]["address"]).to eq(Gitlab::GitalyClient.address(project.repository_storage))
           expect(json_response["gitaly"]["token"]).to eq(Gitlab::GitalyClient.token(project.repository_storage))
-          expect(json_response["gitaly"]["features"]).to eq('gitaly-feature-get-all-lfs-pointers-go' => 'true', 'gitaly-feature-inforef-uploadpack-cache' => 'true', 'gitaly-feature-get-tag-messages-go' => 'true')
+          expect(json_response["gitaly"]["features"]).to eq('gitaly-feature-get-all-lfs-pointers-go' => 'true', 'gitaly-feature-inforef-uploadpack-cache' => 'true', 'gitaly-feature-get-tag-messages-go' => 'true', 'gitaly-feature-filter-shas-with-signatures-go' => 'true')
         end
       end