Cancel previous builds when a new one starts - Self-hosted runners

Problem Definition

At the moment, a self-hosted runner can run one build at a time. Subsequent builds that are triggered get queued until the runner is free to run them. This can often lead to a long queue of builds.

For pipelines that run on branches, some users do not want to wait for older pipelines to finish when a new commit is pushed to the same branch. Instead, it would be preferable to cancel older builds that are still running when there is a new commit on the same branch and run only the latest build.

Similarly, for pipelines that run in pull requests, some users would prefer if a new pull request build cancels any builds on the same pull request that are still running, and run only the latest one.

Suggested Solution

Provide an option to users that will automatically cancel older pipelines that are still running when a new one is triggered on the same definition.