Trigger Prebuild only when certain files or directories change

Is your feature request related to a problem? Please describe

I'm actually super surprised I didn't find this when searching through the issues.

Triggering a prebuild on every commit can be very heavy. It might help Gitpod's backend infrastructure if users could specify directories and files that can be modified without triggering a prebuild. This is common in CI tools (see Gitlab's rules:changes ). For example, I would specify that changes to the README.md file would not trigger a prebuild.

Describe the behaviour you'd like

Use syntax similar to GitLab CI rules:changes to include or exclude files or directories from triggering prebuilds.

Start by locating Gitpod's prebuild trigger entry point and the existing tests around prebuild scheduling; the issue does not name specific files. Compare the current trigger behavior with GitLab's rules:changes semantics, then define how configured file and directory changes determine whether a prebuild runs. Done means the configuration behavior is documented and covered by tests for included, excluded, and unrelated changes.