This document is a reference for the CircleCI 2.x configuration keys that are used in the config.yml file. The presence of a .circleci/config.yml file in your CircleCI-authorized repository branch indicates that you want to use the 2.x infrastructure.You can see a complete config.yml in our full example.Note: If you already have a CircleCI 1.0 configuration, the config.yml file allows you to test 2.x builds on a separate branch, leaving any existing configuration in the old circle.yml style unaffected and running on the CircleCI 1.0 infrastructure in branches that do not contain .circleci/config.yml.
Configuring CircleCI - CircleCI