Common + specific functionality per branch for Bitbucket pipeline

[laurentrivard]

We're creating our pipeline files to build docker images and push to repositories, but we have 3 environments, so three docker repos. 

Each branch needs to configure the environement variables (different credentials, repository urls, etc), but there are common commands that need to run once the variables have been set. Is it possible to have specific commands for each branch and then common functionality that each branch executes? Something like this below: 

pipelines:

  alpha:

    - step:

        -DOCKERFILE=Dockerfile_alpha

        - ACCESS_KEY=Access_key_alpha

        - DOCKER_REPO=alpha_repo...

  production:

    - step:

        -DOCKERFILE=Dockerfile_production

        - ACCESS_KEY=Access_key_production

        - DOCKER_REPO=production_repo...

default:

   #this should execute for any branch, but after the branch specific commands

    - DOCKER push --access-key $ACCESS_KEY --url $DOCKER-REPO

[webfxmasta]

I would also like to define different environment variable values per branch.  I don't need the "common functionality" part, but I do need to be able to define different, secured environment variable values per branch.