Filter _Template content. Resolves #1603 and #1640. (#1612)

* Filter _Template content. Resolves #1603 and #1640.

* Introduces a Gollum::TemplateFilter class with methods to easily add _Template Filters.

* Adds support for relative _Template pages with fallback to _Template in root.

bin/gollum

@@ -152,7 +152,7 @@ MSG
   opts.on('--template-dir [PATH]', 'Specify custom mustache template directory.') do |path|
     wiki_options[:template_dir] = path
   end
-  opts.on('--template-page', 'Use _Template in root as a template for new pages.') do
+  opts.on('--template-page', 'Use _Template.{ext} as a template for new pages.') do
     wiki_options[:template_page] = true
   end
   opts.on('--lenient-tag-lookup', 'Internal links resolve case-insensitively, will treat spaces as hyphens, and will match the first page found with a certain filename, anywhere in the repository. Provides compatibility with Gollum 4.x.') do

lib/gollum.rb

@@ -33,4 +33,20 @@ module Gollum
       super(message || "Cannot write #{@dir}/#{@attempted_path}, found #{@dir}/#{@existing_path}.")
     end
   end
+  
+  class TemplateFilter
+    @@filters = {}
+
+    def self.add_filter(pattern, &replacement)
+      @@filters[pattern] = replacement
+    end
+
+    def self.apply_filters(data)
+      @@filters.each do |pattern, replacement|
+        data.gsub!(pattern, replacement.call)
+      end
+      data
+    end
+  end
+
 end

lib/gollum/app.rb

@@ -351,14 +351,11 @@ module Precious
 
       get '/create/*' do
         forbid unless @allow_editing
-        if settings.wiki_options[:template_page] then
-          temppage = wiki_page('/_Template')
-          @template_page = (temppage.page != nil) ? temppage.page.raw_data : 'Template page option is set, but no /_Template page is present or committed.'
-        end
         wikip = wiki_page(params[:splat].first)
         @name = wikip.name
         @ext  = wikip.ext
         @path = wikip.path
+        @template_page = load_template(@path) if settings.wiki_options[:template_page]
         @allow_uploads = wikip.wiki.allow_uploads
         @upload_dest   = find_upload_dest(wikip.fullpath)
 
@@ -638,6 +635,11 @@ module Precious
       end
     end
 
+    def load_template(path)
+      template_page = wiki_page(::File.join(path, '_Template')).page || wiki_page('/_Template').page
+      template_page ? Gollum::TemplateFilter.apply_filters(template_page.raw_data) : nil
+    end
+
     def update_wiki_page(wiki, page, content, commit, name = nil, format = nil)
       return if !page ||
           ((!content || page.raw_data == content) && page.format == format)