Symfony 2 multiple versions in the same app

We have a symfony 2 project and the client wants 3 "little" different versions of the same app. I would want to avoid creating 3 branches and maintain them separately, so based on the client request I would want to ask you what do you think will be the best approach for that. I studied a little bit, but unsure about the best solution.

So, what client wants:

• dynamic form fields + validation - for every version I will have a different fields configuration. I'm deploying with capistrano, I have a post:deploy command I can hook into that to get fields settings. The problem here is that I have the install context just in that command --version=v1. And I would need in all the app to have a list [v1, v2, v3] and a current v2. What is the best approach to inject a list and a current version in the container ?

Compiling the container with extra parameters ?

Different AppKernel versions ?

• static php files I can handle them using version in path to the files on the deploy command.

Thanks.