[The Repositories' compare method](https://docs.gitlab.com/ee/api/repositories.html#compare-branches-tags-or-commits) expose a query param named `straight` which seems not to be implented yet : https://github.com/gmessner/gitlab4j-api/blob/537849206e38b20c08ce39a845733f68a1d21dfa/src/main/java/org/gitlab4j/api/RepositoryApi.java#L672-L687