What is a rock solid development and deployment workflow? [closed]

Have a look at trellis and bedrock at https://roots.io/, it’s open source.

Bedrock allows you to manage wordpress plugins via composer.

Trellis is a tool to get you a development and production environment, with ensuring that they behave the same, including deployment workflow.

They even explain the Twelve-Factor App methodology, how it relates to WordPress and how they try to implement it and to what extend.