Export commands deprecated

- Provided examplars of export commands re-implemented using the new
  _query command.
- Implemented export-xml.pl, export-xml.py, export-xml.rb.
- Implemented export-csv.pl.
- Implemented export-yaml.pl.
- Implemented export-ical.pl.

scripts/add-ons/export-ical.pl

@@ -0,0 +1,91 @@
+#! /usr/bin/perl
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+## All rights reserved.
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 2 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+## FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, write to the
+##
+##     Free Software Foundation, Inc.,
+##     51 Franklin Street, Fifth Floor,
+##     Boston, MA
+##     02110-1301
+##     USA
+##
+################################################################################
+
+use strict;
+use warnings;
+use JSON;
+
+# Use the taskwarrior 1.9.4+ _query command to issue a query and return JSON
+my $command = '/usr/local/bin/task _query ' . join (' ', @ARGV);
+
+# Generate output.
+print "BEGIN:VCALENDAR\n",
+      "VERSION:2.0\n",
+      "PRODID:=//GBF/taskwarrior 1.9.4//EN\n";
+
+for my $task (split /,$/ms, qx{$command})
+{
+  my $data = from_json ($task);
+
+  print "BEGIN:VTODO\n";
+  print "UID:$data->{'uuid'}\n";
+  print "DTSTAMP:$data->{'entry'}\n";
+  print "DTSTART:$data->{'start'}\n" if exists $data->{'start'};
+  print "DUE:$data->{'due'}\n"       if exists $data->{'due'};
+  print "COMPLETED:$data->{'end'}\n" if exists $data->{'end'};
+  print "SUMMARY:$data->{'description'}\n";
+  print "CLASS:PRIVATE\n";
+  print "CATEGORIES:", join (',', @{$data->{'tags'}}), "\n" if exists $data->{'tags'};
+
+  # Priorities map to a 1-9 scale.
+  if (exists $data->{'priority'})
+  {
+    print "PRIORITY:", ($data->{'priority'} eq 'H' ? '1' :
+                        $data->{'priority'} eq 'M' ? '5' :
+                                                     '9'), "\n";
+  }
+
+  # Status maps differently.
+  my $status = $data->{'status'};
+  if ($status eq 'pending' || $status eq 'waiting')
+  {
+    print "STATUS:", (exists $data->{'start'} ? 'IN-PROCESS' : 'NEEDS-ACTION'), "\n";
+  }
+  elsif ($status eq 'completed')
+  {
+    print "STATUS:COMPLETED\n";
+  }
+  elsif ($status eq 'deleted')
+  {
+    print "STATUS:CANCELLED\n";
+  }
+
+  # Annotations become comments.
+  if (exists $data->{'annotations'})
+  {
+    print "COMMENT:$_->{'description'}\n" for @{$data->{'annotations'}};
+  }
+
+  print "END:VTODO\n";
+}
+
+print "END:VCALENDAR\n";
+exit 0;
+
+################################################################################
+