Fix error 500 when viewing commit and merge request diffs

Due to the refactoring in !16082, `Blob#batch` no longer falls back
to a default `blob_size_limit`. Since `Repository#batch_blobs` was using
a default `nil` value, this would cause issues in the `Blob#find_by_rugged`
method.

This fix here is to be consistent and use a non-nil default value in
`Repository#batch_blobs`.

The problem was masked in development and tests because Gitaly is always
enabled by default for all features.

Closes #41735

1 files changed, 14 insertions, 0 deletions

diff --git a/spec/lib/gitlab/diff/file_collection/merge_request_diff_spec.rb b/spec/lib/gitlab/diff/file_collection/merge_request_diff_spec.rb
index d81774c8b8f..a067c42b75b 100644
--- a/spec/lib/gitlab/diff/file_collection/merge_request_diff_spec.rb
+++ b/spec/lib/gitlab/diff/file_collection/merge_request_diff_spec.rb
@@ -19,4 +19,18 @@ describe Gitlab::Diff::FileCollection::MergeRequestDiff do
 
     diff_files
   end
+
+  shared_examples 'initializes a DiffCollection' do
+    it 'returns a valid instance of a DiffCollection' do
+      expect(diff_files).to be_a(Gitlab::Git::DiffCollection)
+    end
+  end
+
+  context 'with Gitaly disabled', :disable_gitaly do
+    it_behaves_like 'initializes a DiffCollection'
+  end
+
+  context 'with Gitaly enabled' do
+    it_behaves_like 'initializes a DiffCollection'
+  end
 end