Add an "empty" template and let template classes override the "Gemfile" template.

Custom template classes can define "self.gemfile_template" to return the path to their own Gemfile template, without having to reimplement our generate_bundler! task.

CHANGELOG.md

@@ -22,6 +22,8 @@
 3.1.0.rc.1
 ===
 
+* Custom template classes can now override the file used for creating the project Gemfile.
+* Add an "empty" template that produces the minimum necessary structure for a Middleman project.
 * Fix ignoring layouts from the sitemap when the source directory has been set to something other than 'source'. #896
 * Move more into core, autoloaded if gems are available.
 * DataStore may now be accessed like a hash with #[] and #has_key?. #880

middleman-core/lib/middleman-core/templates.rb

@@ -34,6 +34,12 @@ module Middleman::Templates
       source_paths << File.join(File.dirname(__FILE__), 'templates')
     end
 
+    # The gemfile template to use. Individual templates can define this class
+    # method to override the template path.
+    def self.gemfile_template
+      "shared/Gemfile.tt"
+    end
+
     # Required path for the new project to be generated
     argument :location, :type => :string
 
@@ -57,7 +63,7 @@ module Middleman::Templates
     # @return [void]
     def generate_bundler!
       return if options[:'skip-gemfile']
-      template "shared/Gemfile.tt", File.join(location, "Gemfile")
+      template self.class.gemfile_template, File.join(location, "Gemfile")
 
       return if options[:'skip-bundle']
       inside(location) do
@@ -90,4 +96,7 @@ require "middleman-core/templates/mobile"
 require "middleman-more/templates/smacss"
 
 # Local templates
-require "middleman-core/templates/local"
+require "middleman-core/templates/local"
+
+# Barebones template
+require "middleman-core/templates/empty"

middleman-core/lib/middleman-core/templates/empty.rb

@@ -0,0 +1,23 @@
+# A barebones template with nothing much in it
+class Middleman::Templates::Empty < Middleman::Templates::Base
+
+  # Template files are relative to this file
+  # @return [String]
+  def self.source_root
+    File.dirname(__FILE__)
+  end
+
+  def self.gemfile_template
+    "empty/Gemfile.tt"
+  end
+
+  # Actually output the files
+  # @return [void]
+  def build_scaffold!
+    create_file File.join(location, "config.rb"), "\n"
+    empty_directory File.join(location, "source")
+  end
+end
+
+# Register this template
+Middleman::Templates.register(:empty, Middleman::Templates::Empty)

middleman-core/lib/middleman-core/templates/empty/Gemfile.tt

@@ -0,0 +1,3 @@
+source 'https://rubygems.org'
+
+gem "middleman", "~><%= Middleman::VERSION %>"