allow configuring template directive characters

When we're writing blog posts about Perl, we run afoul of the template
parser, a lot. The `%` that indicates a line of template is the same as
the hash sigil, which often appears on the start of a line.

Now, users can disable line-based processing entirely if they want, and
change the template tags to look however they want (maybe to match
Template Toolkit, so `[% ... %]`).

Refs preaction#541

lib/Statocles/Template.pm

@@ -78,8 +78,21 @@ has _template => (
     lazy => 1,
     default => sub {
         my ( $self ) = @_;
+        my %config;
+        if ( $self->theme ) {
+            %config = map { $_ => $self->theme->$_ }
+                grep { $self->theme->$_ }
+                qw(
+                    tag_start tag_end
+                    line_start trim_mark
+                    replace_mark expression_mark
+                    escape_mark comment_mark
+                    capture_start capture_end
+                );
+        }
         my $t = Mojo::Template->new(
             name => $self->path,
+            %config,
         );
         $t->parse( $self->content );
         return $t;

lib/Statocles/Theme.pm

@@ -45,6 +45,59 @@ has include_stores => (
     },
 );
 
+=attr tag_start
+
+String that indicates the start of a template tag. Defaults to
+C<< <% >>.
+
+=attr tag_end
+
+String that indicates the end of a template tag. Defaults to C<< %> >>.
+
+=attr line_start
+
+String that indicates the start of a line of template code.
+Defaults to C<%>.
+
+=attr expression_mark
+
+String that indicates an expression to be evaluated and inserted into
+the template. Defaults to C<=>.
+
+=attr escape_mark
+
+String that escapes the template directives. Defaults to C<%>.
+
+=attr comment_mark
+
+String that indicates a comment. Defaults to C<#>.
+
+=attr capture_start
+
+Keyword that starts capturing string. Defaults to C<begin>.
+
+=attr capture_end
+
+Keyword that ends capturing string. Defaults to C<end>.
+
+=attr trim_mark
+
+String that indicates that whitespace should be trimmed. Defaults to
+C<=>.
+
+=cut
+
+has [qw(
+    tag_start tag_end
+    line_start trim_mark
+    replace_mark expression_mark
+    escape_mark comment_mark
+    capture_start capture_end
+)] => (
+    is => 'ro',
+    isa => Maybe[Str],
+);
+
 =attr _templates
 
 The cached template objects for this theme.

t/theme/template.t

@@ -205,6 +205,26 @@ ENDHTML
     };
 };
 
+subtest 'template directive config' => sub {
+    my $theme = Statocles::Theme->new(
+        store => '::default',
+        tag_start => '[%',
+        tag_end => '%]',
+        line_start => "\036", # Something nobody will use
+    );
+    my $content = <<ENDTMPL;
+[%= "hello" %]
+% not you
+ENDTMPL
+    my $expect = <<'ENDHTML';
+hello
+% not you
+ENDHTML
+    my $tmpl = $theme->build_template( 'derp', $content );
+    my $got = $tmpl->render;
+    eq_or_diff $got, $expect;
+};
+
 subtest 'error messages' => sub {
 
     subtest 'template not found' => sub {