WIP: Add 'jekyll new-theme' command

lib/jekyll/commands/new_theme.rb

@@ -0,0 +1,82 @@
+require 'erb'
+
+module Jekyll
+  module Commands
+    class NewTheme < Command
+      class << self
+        def init_with_program(prog)
+          prog.command(:"new-theme") do |c|
+            c.syntax 'new-theme NAME'
+            c.description 'Creates a new Jekyll theme scaffold'
+
+            c.action do |args, _|
+              Jekyll::Commands::NewTheme.process(args)
+            end
+          end
+        end
+
+        def process(args)
+          raise InvalidThemeName, 'You must specify a theme name.' if args.empty?
+
+          new_theme_name = args.join("_")
+          theme = ThemeBuilder.new(new_theme_name)
+          if theme.path.exist?
+            Jekyll.logger.abort_with "Conflict:", "#{theme.path} already exists."
+          end
+
+          theme.create!
+          Jekyll.logger.info "Your new Jekyll theme, #{theme.name} is ready for you in #{theme.path}."
+        end
+
+        class ThemeBuilder
+          attr_reader :name, :path
+          def initialize(theme_name)
+            @name = theme_name
+            @path = Pathname.new(File.expand_path(theme_name, Dir.pwd))
+          end
+
+          def create!
+            create_directories
+            create_gemspec
+            create_readme
+          end
+
+          private
+
+          def create_directories
+            Dir.chdir(path) do
+              FileUtils.mkdir_p(%w{_includes _layouts _sass})
+            end
+          end
+        end
+
+        private
+
+        def gemfile_contents
+          <<-RUBY
+source "https://rubygems.org"
+
+# Hello! This is where you manage which Jekyll version is used to run.
+# When you want to use a different version, change it below, save the
+# file and run `bundle install`. Run Jekyll with `bundle exec`, like so:
+#
+#     bundle exec jekyll serve
+#
+# This will help ensure the proper Jekyll version is running.
+# Happy Jekylling!
+gem "jekyll", "#{Jekyll::VERSION}"
+
+# If you want to use GitHub Pages, remove the "gem "jekyll"" above and
+# uncomment the line below. To upgrade, run `bundle update github-pages`.
+# gem "github-pages", group: :jekyll_plugins
+
+# If you have any plugins, put them here!
+# group :jekyll_plugins do
+#   gem "jekyll-github-metadata", "~> 1.0"
+# end
+RUBY
+        end
+      end
+    end
+  end
+end