OpamFile.PkgListA simple list of packages and versions: (used for the older $opam/$switch/{installed,installed_roots}, still needed to migrate from 1.2 repository, and for reinstall)
type t = OpamTypes.package_setFile contents
val format_version : OpamVersion.tval empty : tEmpty file
val write : t typed_file -> t -> unitWrite some contents to a file
val read : t typed_file -> tRead file contents. Raise an error if the file does not exist.
val read_opt : t typed_file -> t optionReturns None on non-existing file
val safe_read : t typed_file -> tRead file contents. Return empty if the file does not exist.
val read_from_channel : ?filename:t typed_file -> in_channel -> tval read_from_string : ?filename:t typed_file -> string -> tval write_to_channel : ?filename:t typed_file -> out_channel -> t -> unitval write_to_string : ?filename:t typed_file -> t -> string