Cancel build on branch when new commit added

In our case - running all tests on single commit taking ~10-15 mins. People sometimes are pushing new and new commits to the same branch, as result - tests are executed on different commits on the same branch in parallel.

In order to optimize used build minutes I’d like to have ability to enable cancelling builds on branch when new commit was added, for instance Travis doing in this way.

In order to not brake builds that are expected to be ran in parallel - we could cancel builds that were triggered automatially, not manually.