Problem description

In our bitbucket-pipelines, we define a pipeline to run on a pull request for every `feature/*` branch.

We open a pull request to merge branch `feature/A` into master, and pipelines are triggered fine for every pushed commit.

Since feature A is a very big feature, a coworker decides to help, and branches of `feature/A2` from `feature/A`.

Feature A2 is ready, so we decide to merge `feature/A2` into `feature/A`. This adds a merge commit on top of `feature/A`, but a pipeline is not triggered.

Now if I merge `feature/A2` into `feature/A` locally, and then push the merge commit, the PR pipeline does trigger.

Expected behavior

A pipeline is triggered for every change in the source branch of the PR.

Actual behavior

A merge via BitBucket into the source branch of an open PR does not trigger the pipeline registered for that PR.