On the Dutch Web Alliance site today they've posted a tutorial about their use of Capifony for Symfony application deployment and how it relates to updating the "parameter.yml" file. They describe their current deployment process, how it works with the different environments and how they solved the one manually problem they had.

The actual deployment is thus dealt with by capifony. This is a plugin for capistrano written for deploying Symfony applications. [...] Capifony automatically deals with cloning the correct branch on the servers, installing dependencies through composer, migrating database versions etc etc. Basically we don’t have to care about anything else. However, there is one single thing that still keeps on bugging us: when we want to upgrade to a new parameters.yml, we must do this manually. This means that our builds will break when we deploy a version that requires an updated parameters.yml until we manually solve the issue.

To get around this manual issue, they decided on creating a new Capifony task that does an upload/download of the parameters file, depending on the environment.The continuous deployment can then push or pull the file as needed in a more automatic way.