Fix merge request diff deserialisation when too_large was absent

Not all diffs in st_diffs had the too_large attribute set at all, but the column
is non-nullable. Explicitly cast to boolean to avoid that problem.

lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits.rb

@@ -85,6 +85,8 @@ module Gitlab
           diff_hash.tap do |hash|
             diff_text = hash[:diff]
 
+            hash[:too_large] = !!hash[:too_large]
+
             if diff_text.encoding == Encoding::BINARY && !diff_text.ascii_only?
               hash[:binary] = true
               hash[:diff] = [diff_text].pack('m0')

spec/lib/gitlab/background_migration/deserialize_merge_request_diffs_and_commits_spec.rb

@@ -123,6 +123,17 @@ describe Gitlab::BackgroundMigration::DeserializeMergeRequestDiffsAndCommits do
       include_examples 'updated MR diff'
     end
 
+    context 'when the merge request diffs do not have too_large set' do
+      let(:commits) { merge_request_diff.commits.map(&:to_hash) }
+      let(:expected_diffs) { diffs_to_hashes(merge_request_diff.merge_request_diff_files) }
+
+      let(:diffs) do
+        expected_diffs.map { |diff| diff.except(:too_large) }
+      end
+
+      include_examples 'updated MR diff'
+    end
+
     context 'when the merge request diffs have binary content' do
       let(:commits) { merge_request_diff.commits.map(&:to_hash) }
       let(:expected_diffs) { diffs }