I looked into gruntjs but I'm not sure if it the right tool to solve my workflow problem. I' working on a huge angular project with 30+ js files already into it. Every time I add a new js file, I have to go to index file and add reference in it. Is there any way to automate this process with grunt or any other tool?
Absolutely! Here are two ways:
Yeoman is a set of integrated workflow management scripts built on Grunt and Bower that supports automatic scaffolding and compilation. There is an AngularJS generator for it too.
This is my creation, so I definitely have a bias here, but it has a Grunt-based built system and a defined directory structure that makes managing non-trivial AngularJS apps super easy.