add includeRegenerator option

bin/6to5/index.js

@@ -25,6 +25,7 @@ commander.option("-I, --indent [width]", "Indent width [2]", 2);
 commander.option("-a, --amd-module-ids", "Insert module id in AMD modules", false); // todo: remove in 3.0.0
 commander.option("-m, --module-ids", "Insert module id in modules", false);
 commander.option("-R, --react-compat", "Makes the react transformer produce pre-v0.12 code");
+commander.option("-E, --include-regenerator", "Include the regenerator runtime if necessary", false);
 
 commander.on("--help", function(){
   var outKeys = function (title, obj) {
@@ -100,8 +101,10 @@ if (errors.length) {
 //
 
 exports.opts = {
+  includeRegenerator: commander.includeRegenerator,
   sourceMapName:      commander.outFile,
   experimental:       commander.experimental,
+  reactCompat:        commander.reactCompat,
   playground:         commander.playground,
   moduleIds:          commander.amdModuleIds || commander.moduleIds,
   blacklist:          commander.blacklist,
@@ -111,7 +114,6 @@ exports.opts = {
   comments:           !commander.removeComments,
   runtime:            commander.runtime,
   modules:            commander.modules,
-  reactCompat:   commander.reactCompat,
   format: {
     indent: {
       style:     util.repeat(parseInt(commander.indent))

lib/6to5/file.js

@@ -48,6 +48,7 @@ File.normaliseOptions = function (opts) {
   opts = _.cloneDeep(opts || {});
 
   _.defaults(opts, {
+    includeRegenerator: false,
     experimental:       false,
     reactCompat:        false,
     playground:         false,

lib/6to5/transformation/transformers/es6-generators.js

@@ -1,3 +1,9 @@
+var regenerator = require("regenerator");
+
 exports.ast = {
-  before: require("regenerator").transform
+  before: function (ast, file) {
+    regenerator.transform(ast, {
+      includeRuntime: file.opts.includeRegenerator && "if used"
+    });
+  }
 };