gemfile entries can be added to the app builder

railties/lib/rails/generators/app_base.rb

@@ -77,14 +77,26 @@ module Rails
       end
 
       def initialize(*args)
-        @original_wd = Dir.pwd
-        @gem_filter = lambda { |gem| true }
+        @original_wd   = Dir.pwd
+        @gem_filter    = lambda { |gem| true }
+        @extra_entries = []
         super
         convert_database_option_for_jruby
       end
 
     protected
 
+      def gemfile_entry(name, version = nil, github: nil, path: nil)
+        if github
+          @extra_entries << GemfileEntry.github(name, github)
+        elsif path
+          @extra_entries << GemfileEntry.path(name, path)
+        else
+          @extra_entries << GemfileEntry.version(name, version)
+        end
+        self
+      end
+
       def gemfile_entries
         [ rails_gemfile_entry,
           database_gemfile_entry,
@@ -92,7 +104,8 @@ module Rails
           javascript_gemfile_entry,
           jbuilder_gemfile_entry,
           webconsole_gemfile_entry,
-          sdoc_gemfile_entry].flatten.find_all(&@gem_filter)
+          sdoc_gemfile_entry,
+          @extra_entries].flatten.find_all(&@gem_filter)
       end
 
       def add_gem_entry_filter

railties/test/generators/generator_test.rb

@@ -14,6 +14,7 @@ module Rails
             def gemfile_entries; super; end
             def invoke_all; super; self; end
             def add_gem_entry_filter; super; end
+            def gemfile_entry(*args); super; end
           })
         end
       end
@@ -23,6 +24,40 @@ module Rails
         assert klass.start(['new', 'blah'])
       end
 
+      def test_add_gem
+        klass = make_builder_class
+        generator = klass.start(['new', 'blah'])
+        generator.gemfile_entry 'tenderlove'
+        assert_includes generator.gemfile_entries.map(&:name), 'tenderlove'
+      end
+
+      def test_add_gem_with_version
+        klass = make_builder_class
+        generator = klass.start(['new', 'blah'])
+        generator.gemfile_entry 'tenderlove', '2.0.0'
+        assert generator.gemfile_entries.find { |gfe|
+          gfe.name == 'tenderlove' && gfe.version == '2.0.0'
+        }
+      end
+
+      def test_add_github_gem
+        klass = make_builder_class
+        generator = klass.start(['new', 'blah'])
+        generator.gemfile_entry 'tenderlove', github: 'hello world'
+        assert generator.gemfile_entries.find { |gfe|
+          gfe.name == 'tenderlove' && gfe.options[:github] == 'hello world'
+        }
+      end
+
+      def test_add_path_gem
+        klass = make_builder_class
+        generator = klass.start(['new', 'blah'])
+        generator.gemfile_entry 'tenderlove', path: 'hello world'
+        assert generator.gemfile_entries.find { |gfe|
+          gfe.name == 'tenderlove' && gfe.options[:path] == 'hello world'
+        }
+      end
+
       def test_filter
         klass     = make_builder_class
         generator = klass.start(['new', 'blah'])