let parse_packages_in ?filter ?(archs=[]) ?(extras=[]) file ic =
info "Parsing Packages file %s..." file;
try
let stanza_parser = parse_package_stanza filter archs extras in
Format822.parse_from_ch (packages_parser stanza_parser []) ic
with ParseError (field,errmsg) -> fatal "Filename %s\n %s : %s" file field errmsg