As some opened discussions are showing:
I would like to be able to trigger a new build on a pull request, since every commit can get validated, there are deployment commands that I would like to get launched on a PR for QA purposes (like generating a build with the change being purposed for testing).
This feature is complimentary to this bug report: CI_PULL_REQUEST no longer when building a PR
Since I could be adding commits to my branch before creating the PR, that environment variable is simply not enough, I would need another build on PR generation.
As mentioned in other threads, TravisCI has this option and is really useful