Create an Environment when environment switch is given

Author: Calum Gilchrist

lib/octocatalog-diff/catalog-util/builddir.rb

@@ -85,7 +85,7 @@ def create_symlinks(logger = nil)
           end
         else
           if @options[:environment]
-            logger.warn '--environment is ignored unless --preserve-environments is used' unless logger.nil?
+            install_directory_symlink(logger, @options[:basedir], "environments/#{@options[:environment]}")
           end
           if @options[:create_symlinks]
             logger.warn '--create-symlinks is ignored unless --preserve-environments is used' unless logger.nil?