OpamRepository.BACKEND

`sig val pull_url : OpamTypes.package -> OpamTypes.dirname -> string option -> OpamTypes.address -> OpamTypes.generic_file OpamTypes.download OpamProcess.job val pull_repo : OpamTypes.repository -> unit OpamProcess.job val pull_archive : OpamTypes.repository -> OpamTypes.filename -> OpamTypes.filename OpamTypes.download OpamProcess.job val revision : OpamTypes.repository -> OpamTypes.version option OpamProcess.job end`