Batchload blobs for diff generation

After installing a new gem, batch-loader, a construct can be used to
queue data to be fetched in bulk. The gem was also introduced in both
gitlab-org/gitlab-ce!14680 and gitlab-org/gitlab-ce!14846, but those mrs
are not merged yet.

For the generation of diffs, both the old blob and the new blob need to
be loaded. This for every file in the diff, too. Now we collect all
these so we do 1 fetch. Three `.allow_n_plus_1_calls` have been removed,
which I expect to be valid, but this needs to be confirmed by a full CI
run.

Possibly closes:
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37445
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37599
- https://gitlab.com/gitlab-org/gitlab-ce/issues/37431

1 files changed, 2 insertions, 0 deletions

diff --git a/Gemfile b/Gemfile
index 5630f91c054..6034323956c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -263,6 +263,8 @@ gem 'gettext_i18n_rails', '~> 1.8.0'
 gem 'gettext_i18n_rails_js', '~> 1.2.0'
 gem 'gettext', '~> 3.2.2', require: false, group: :development
 
+gem 'batch-loader'
+
 # Perf bar
 gem 'peek', '~> 1.0.1'
 gem 'peek-gc', '~> 0.0.2'