add tzoffset shim method

This should allow users time to fix their templates, along with
instructions on how to do so.

Refs #461

lib/Statocles/Help/Upgrading.pod

@@ -76,27 +76,26 @@ without bells and whistles, the Basic app can be used.
 
 The Static app will be removed in v2.000.
 
-=back
-
-=head1 BREAKING CHANGES
-
-=head2 v0.070
-
-=over 4
-
-=item Error in template: Can't locate object method "tzoffset" via package "DateTime::Moonpig"
+=item The tzoffset shim method will be removed in Statocles version 2.0.
 
 In order to allow documents dated before 1900, Statocles is now using
 a different date/time library, L<DateTime::Moonpig>. This new library
 is mostly compatible, except for the the C<tzoffset> method, which is
 used by the RSS feed because it uses the RFC822 date format.
 
+Statocles adds a shim method that replicates the functionality, but it
+is a better idea to fix your templates to use the correct method.
+
 To fix this, copy the C<blog/index.rss.ep> template from the default
 theme, or change C<$p-E<gt>date-E<gt>tzoffset / 36> in the C<pubDate>
 tag to C<$p-E<gt>date-E<gt>offset / 3600>.
 
+Deprecated in v0.070. Will be removed in v2.000.
+
 =back
 
+=head1 BREAKING CHANGES
+
 =head2 v0.055
 
 =over 4

lib/Statocles/Types.pm

@@ -71,6 +71,12 @@ coerce DateTimeObj, from DateTimeStr, via {
     );
 };
 
+sub DateTime::Moonpig::tzoffset {
+    my ( $self ) = @_;
+    warn "The tzoffset shim method will be removed in Statocles version 2.0. See Statocles::Help::Upgrading for instructions to remove this warning.\n";
+    return $self->offset * 100;
+}
+
 # Down here to resolve circular dependencies
 require Statocles::Store;
 require Statocles::Link;

t/deprecated.t

@@ -156,4 +156,21 @@ subtest 'Statocles::App::Static' => sub {
     }
 };
 
+subtest 'tzoffset shim' => sub {
+    use Statocles::Types qw( DateTimeObj );
+    if ( $Statocles::VERSION < 2 ) {
+        my $dt = DateTimeObj->coerce( '2015-01-01' );
+        ok $dt->can( 'tzoffset' ), 'tzoffset method exists';
+
+        my @warnings;
+        local $SIG{__WARN__} = sub { push @warnings, @_ };
+        is $dt->tzoffset, 0, 'tzoffset is correct';
+        like $warnings[0], qr{\QThe tzoffset shim method will be removed in Statocles version 2.0. See Statocles::Help::Upgrading for instructions to remove this warning.}, 'warn on tzoffset method';
+    }
+    else {
+        my $dt = DateTimeObj->coerce( '2015-01-01' );
+        ok !$dt->can( 'tzoffset' ), 'tzoffset method does not exist';
+    }
+};
+
 done_testing;