As of today Tuleap uses a Docker image (
https://tuleap.net/plugins/git/tuleap/docker/tuleap-generated-files-builder) to build the sources.
This image is maintained out of the main source tree so we have no guarantee that if we try to build an old version of Tuleap it will still work. We also have no guarantee that the image will not change in a way that could impact the build of the production packages. Only a few tool are pinned to a specific but pinning everything in the Docker image is a tedious job and it's also not easy to maintain.
The same tools (+ a few others) are also needed in a dev environment but as of today it is the responsibility of each developers to maintain an environment close enough to the real one so they can can build the sources. It often leads to issue when a tool needs to be upgraded because each developer needs to understand what's the error and how to upgrade. The problem is even bigger for developers on macOS since their base tools might not be GNU compatible (e.g.
request #15080).
The goal of this request is to provide a solution that could work for both situations.