+# returns undef on failure, number on success
+sub group2folders {
+ my ($self, $lei, $all, $folders) = @_;
+ return $lei->fail(<<EOM) if @$folders;
+--all= not compatible with @$folders on command-line
+EOM
+ my %x = map { $_ => $_ } split(/,/, $all);
+ my @ok = grep(defined, delete(@x{qw(local remote), ''}));
+ my @no = keys %x;
+ if (@no) {
+ @no = (join(',', @no));
+ return $lei->fail(<<EOM);
+--all=@no not accepted (must be `local' and/or `remote')
+EOM
+ }
+ my (%seen, @inc);
+ my @all = $self->folders;
+ for my $ok (@ok) {
+ if ($ok eq 'local') {
+ @inc = grep(!m!\A[a-z0-9\+]+://!i, @all);
+ } elsif ($ok eq 'remote') {
+ @inc = grep(m!\A[a-z0-9\+]+://!i, @all);
+ } elsif ($ok ne '') {
+ return $lei->fail("--all=$all not understood");
+ } else {
+ @inc = @all;
+ }
+ for (@inc) {
+ push(@$folders, $_) unless $seen{$_}++;
+ }
+ }
+ scalar(@$folders) || $lei->fail(<<EOM);
+no --mail-sync folders known to lei
+EOM
+}
+