Comment Out a replace

[combmag-zz]

Image i have this index.html

<!-- build:dev -->
<script src=angular.js></script>
<script src=app.js></script>
<!--endbuild -->

<!-- build:prod -->
<!-- <script src=bundle.js></script> -->
<!--endbuild -->

it would be nice if i can have a task to specify to comment out the section of build dev and uncomment the section of build prod so the result would be:

<!-- build:dev -->
<!-- <script src=angular.js></script> -->
<!-- <script src=app.js></script> -->
<!--endbuild -->

<!-- build:prod -->
<script src=bundle.js></script>
<!--endbuild -->

What do you guys think?