first step of the big refactoring ("tree" branch).

From here on, we can track changes. It made no sense to put the
development up to this point into git.

testcases/t/16-nestedcons.t

@@ -0,0 +1,84 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+
+use Test::More tests => 8;
+use Test::Deep;
+use List::MoreUtils qw(all none);
+use Data::Dumper;
+use AnyEvent::I3;
+
+my $i3 = i3("/tmp/nestedcons");
+
+####################
+# Request tree
+####################
+
+my $tree = $i3->get_workspaces->recv;
+# $VAR1 = {
+#           'fullscreen_mode' => 0,
+#           'nodes' => [
+#                         {
+#                           'fullscreen_mode' => 0,
+#                           'nodes' => [
+#                                         {
+#                                           'fullscreen_mode' => 0,
+#                                           'nodes' => [],
+#                                           'window' => undef,
+#                                           'name' => '1',
+#                                           'orientation' => 0,
+#                                           'type' => 2
+#                                         }
+#                                       ],
+#                           'window' => undef,
+#                           'name' => 'LVDS1',
+#                           'orientation' => 0,
+#                           'type' => 1
+#                         }
+#                       ],
+#           'window' => undef,
+#           'name' => 'root',
+#           'orientation' => 0,
+#           'type' => 0
+#         };
+
+my $expected = {
+    fullscreen_mode => 0,
+    nodes => ignore(),
+    window => undef,
+    name => 'root',
+    orientation => ignore(),
+    type => 0,
+    id => ignore(),
+};
+
+cmp_deeply($tree, $expected, 'root node OK');
+
+my @nodes = @{$tree->{nodes}};
+
+ok(@nodes > 0, 'root node has at least one leaf');
+
+ok((all { $_->{type} == 1 } @nodes), 'all nodes are of type CT_OUTPUT');
+ok((none { defined($_->{window}) } @nodes), 'no CT_OUTPUT contains a window');
+ok((all { @{$_->{nodes}} > 0 } @nodes), 'all nodes have at least one leaf (workspace)');
+my @workspaces;
+for my $ws (map { @{$_->{nodes}} } @nodes) {
+    push @workspaces, $ws;
+}
+
+ok((all { $_->{type} == 2 } @workspaces), 'all workspaces are of type CT_CON');
+ok((all { @{$_->{nodes}} == 0 } @workspaces), 'all workspaces are empty yet');
+ok((none { defined($_->{window}) } @workspaces), 'no CT_OUTPUT contains a window');
+
+# TODO: get the focused container
+
+$i3->command('open')->recv;
+
+# TODO: get the focused container, check if it changed.
+# TODO: get the old focused container, check if there is a new child
+
+diag(Dumper(\@workspaces));
+
+diag(Dumper($tree));
+
+
+diag( "Testing i3, Perl $], $^X" );