Follow-up from "Set limits for Projects::CompareController#show"

The following discussions from !201495 (merged) should be addressed:

• @bauerdominic started a discussion:

  suggestion(non-blocking): COMMITS_SAFE_SIZE is 100 so we don't need to mock:

• @bauerdominic started a discussion:

  suggestion(non-blocking): we could avoid recreating the pipeline:

        let_it_be(:to_ref) { '5937ac0a7beb003549fc5fd26fc247adbce4a52e' }
        let(:straight) { "false" }
  
        before_all do
          create(:ci_pipeline, project: project, ref: to_ref)
        end