$OpenBSD: OpenBSD::PkgCfl.pod,v 1.3 2010/06/30 10:51:04 espie Exp $

=head1 NAME

OpenBSD::PkgCfl - C<pkg_create(1)> C<@conflict> handling

=head1 SYNOPSIS

    use OpenBSD::PkgCfl;

    $clist = OpenBSD::PkgCfl->make_conflicts_list($plist);
    @cfls = $clist->conflicts_with(@pkgnames);

    OpenBSD::PkgCfl::register($plist, $state);
    OpenBSD::PkgCfl::unregister($plist, $state);
    @cfls = OpenBSD::PkgCfl::find_all($plist, $state);

=head1 DESCRIPTION

C<OpenBSD::PkgCfl> is the canonical interface to packing-list conflict
handling.

Conflict information can be extracted from a packing-list
(see L<OpenBSD::PackingList>) through the
C<OpenBSD::PkgCfl> class method. The result is an opaque object C<$clist> that
can be queried to find out which package names conflict with the
packing-list.   A query of the form C<$clist-E<gt>conflicts_with(@pkgnames)>
will extract from the list the package names that actually conflict with
the packing-list.

Most handling of conflict information happens through the higher level
interface: C<OpenBSD::PkgCfl::register>, C<OpenBSD::PkgCfl::unregister>
and C<OpenBSD::PkgCfl::find_all>.  Package tools usually handle installed
packages, and this interface automatically takes the initial set of installed
packages into account. The C<register> and C<unregister> functions must
be used to add and remove a packing-list from the set of installed packages,
where conflict information is concerned.

The C<find_all> function can be used to find out about all possible conflicts
a new packing-list will entail, before actually adding the package.

The extra argument C<$state> is a hash used to record system-wide options.
In this case, it acts as a hidden object that records all conflict
information. The hash key C<conflict_list> is reserved for that purpose.