repository: Always use `ListBlobs()` to enumerate new blobs

In 0d5df6f0 (repository: Implement `#new_blobs` via `#list_blobs`,
2021-08-25), we have introduced an alternative implementation of
`#new_blobs` which uses `ListBlobs()` instead of `ListNewBlobs()`. While
there wasn't yet any change in behaviour, this conversion allows us to
convert `#new_blobs` to receive multiple new revisions as arguments such
that we can batch-load new blobs in a single call instead of having to
do so once per change.

Remove the feature flag that has been guarding this new implementation
such that we can continue with the conversion. While the new code has
only been tested in production for one day at the time of writing this
commit, there haven't been any issues. Furthermore, the risk of this
change was low from the beginning. So removing the feature flag this
quickly shouldn't be much of a concern.

Changelog: added

config/feature_flags/development/new_blobs_via_list_blobs.yml

----
-name: new_blobs_via_list_blobs
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/68935
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/339637
-milestone: '14.3'
-type: development
-group: group::gitaly
-default_enabled: false

lib/gitlab/git/repository.rb

@@ -364,13 +364,7 @@ module Gitlab
         return [] if newrev.blank? || newrev == ::Gitlab::Git::BLANK_SHA
 
         strong_memoize("new_blobs_#{newrev}") do
-          if Feature.enabled?(:new_blobs_via_list_blobs)
-            blobs(['--not', '--all', '--not', newrev], with_paths: true, dynamic_timeout: dynamic_timeout)
-          else
-            wrapped_gitaly_errors do
-              gitaly_ref_client.list_new_blobs(newrev, REV_LIST_COMMIT_LIMIT, dynamic_timeout: dynamic_timeout)
-            end
-          end
+          blobs(['--not', '--all', '--not', newrev], with_paths: true, dynamic_timeout: dynamic_timeout)
         end
       end
 

spec/lib/gitlab/git/repository_spec.rb

@@ -959,49 +959,22 @@ RSpec.describe Gitlab::Git::Repository, :seed_helper do
 
     subject { repository.new_blobs(new_commit).to_a }
 
-    context 'with :new_blobs_via_list_blobs enabled' do
-      before do
-        stub_feature_flags(new_blobs_via_list_blobs: true)
-
-        expect_next_instance_of(Gitlab::GitalyClient::BlobService) do |service|
-          expect(service)
-            .to receive(:list_blobs)
-            .with(['--not', '--all', '--not', new_commit],
-                  limit: Gitlab::Git::Repository::REV_LIST_COMMIT_LIMIT,
-                  with_paths: true,
-                  dynamic_timeout: nil)
-            .and_call_original
-        end
-      end
-
-      it 'enumerates new blobs' do
-        expect(subject).to match_array(
-          [have_attributes(class: Gitlab::Git::Blob, id: new_blob, path: 'nested/new-blob.txt', size: 18)]
-        )
+    before do
+      expect_next_instance_of(Gitlab::GitalyClient::BlobService) do |service|
+        expect(service)
+          .to receive(:list_blobs)
+          .with(['--not', '--all', '--not', new_commit],
+                limit: Gitlab::Git::Repository::REV_LIST_COMMIT_LIMIT,
+                with_paths: true,
+                dynamic_timeout: nil)
+          .and_call_original
       end
     end
 
-    context 'with :new_blobs_via_list_blobs disabled' do
-      before do
-        stub_feature_flags(new_blobs_via_list_blobs: false)
-
-        expect_next_instance_of(Gitlab::GitalyClient::RefService) do |service|
-          expect(service)
-            .to receive(:list_new_blobs)
-            .with(new_commit,
-                  Gitlab::Git::Repository::REV_LIST_COMMIT_LIMIT,
-                  dynamic_timeout: nil)
-            .and_call_original
-        end
-      end
-
-      it 'enumerates new blobs' do
-        expect(subject).to match_array([Gitaly::NewBlobObject.new(
-          size: 18,
-          oid: new_blob,
-          path: "nested/new-blob.txt"
-        )])
-      end
+    it 'enumerates new blobs' do
+      expect(subject).to match_array(
+        [have_attributes(class: Gitlab::Git::Blob, id: new_blob, path: 'nested/new-blob.txt', size: 18)]
+      )
     end
   end