Support for parameterised configurations in `.gitpod.yml`

Current Approach

Currently, the way that gitpod works is via one single declarative syntax for a project set up, but, this approach doesn't work well for scenarios where you have (potentially) many different permutations of a given project or setup (e.g. mono-repo's or more advanced projects). Currently, the best way of doing this is via URL parameters or via environment variables that alter the project configuration, in combination with custom scripts and/or a makefile.

Proposal

Allow a given project to specify a number of input parameters (type definitions and optionality) for a project configuration. This feature would then allow the creation of any number of different permutations of a given project (e.g. a matrix), and a project or workspace. Each permutation of the matrix is then treated as it's own "project" configuration e.g. it has it's own pre-build and allows custom start tasks to be configured. A good real example of this is the DrupalPod project, which uses a Chrome extension to specify input parameters, that are passed via URL, and then consumed in scripts to create different set-ups of the project.

Examples

Example of this within DrupalPod, which uses a browser extension form [1].

Similar feature in other products

• https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#inputs
• https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstrategymatrix
• https://www.serverless.com/framework/docs/guides/parameters
• https://docs.travis-ci.com/user/build-matrix/
• https://circleci.com/blog/circleci-matrix-jobs/
• https://0-8-0.docs.drone.io/matrix-builds/

Start by reading the proposed .gitpod.yml configuration model and the linked DrupalPod and matrix examples. Identify the configuration, workspace, pre-build, and start-task entry points before defining the scope. Done means parameter types and optionality can produce distinct project configurations with their own pre-builds and start tasks, backed by tests for the supported permutations.