use File::Path;

    registerRoot getGCRootsDir

}
sub getGCRootsDir {
    die unless defined $ENV{LOGNAME};
    return "/nix/var/nix/gcroots/per-user/$ENV{LOGNAME}/hydra-roots";
}
sub registerRoot {
    my ($path) = @_;
    my $gcRootsDir = getGCRootsDir;
    
    mkpath($gcRootsDir) if !-e $gcRootsDir;
    my $link = "$gcRootsDir/" . basename $path;
        
    if (!-l $link) {
        symlink($path, $link)
            or die "cannot create symlink in $gcRootsDir to $path";
    }

    
    registerRoot $outPath;

        # !!! this should really by done by nix-instantiate to prevent a GC race.
        registerRoot $drvPath;

die unless defined $ENV{LOGNAME};
my $gcRootsDir = "/nix/var/nix/gcroots/per-user/$ENV{LOGNAME}/hydra-roots";

    #print "$path\n";
    mkpath($gcRootsDir) if !-e $gcRootsDir;
    my $link = "$gcRootsDir/" . basename $path;
        
    if (!-l $link) {
        symlink($path, $link)
            or die "cannot create symlink in $gcRootsDir to $path";
    }

    Hydra::Helper::Nix::registerRoot($path);

# For scheduled builds, we register the derivation as a GC root.

# For scheduled builds, we register the derivation and the output as a GC root.

        print "keeping scheduled build ", $build->id, " (",
            strftime("%Y-%m-%d %H:%M:%S", localtime($build->timestamp)), ")\n";

        registerRoot $build->outpath;

print "*** removing unneeded GC roots\n";
my $gcRootsDir = getGCRootsDir;