Scheduled repository polling in Pipelines

Problem Definition

Scheduled pipelines allow users to run a pipeline at hourly, daily or weekly intervals.
The pipeline will always run at the scheduled time frame, even if there are no changes in the repository since the last build.

This is not always desirable. One use case where this is not ideal is the following:

The problem here is that we are using the build number for versioning. The pipeline is using this value to inject into the code and also to tag the repository. We don't want to run a build (which generates a new build number) unless there are changes in the repository.

Additionally, users may not want to consume build minutes for a scheduled build, if there are no changes in the repo.

Suggested Solution

Support scheduled repository polling, similar to Bamboo:

https://confluence.atlassian.com/bamboo/repository-polling-289276903.html

Provide an option in the schedules that will poll the repository for changes, and then trigger a build only if there are changes.