Why doesn't bitbucket pipelines on 'pull-requests' perform a merge on Target Branch?

[Luis Duarte]

e.g.:

pipelines:
  pull-requests:
    '**':
      - step:
          script:
            - npm install
            - npm run lint
            - npm run build

I want this to do a `git merge --no-ff $TARGET_BRANCH` before running the build.

How is this possible? 

[mwatson]

Hi Luis,

We merge the target branch to the source branch when running pull-requests builds, as per https://confluence.atlassian.com/bitbucket/configure-bitbucket-pipelines-yml-792298910.html#Configurebitbucket-pipelines.yml-ci_pull-requestspull-requests

This type of pipeline runs a little differently to other pipelines. When it's triggered, we'll merge the destination branch into your working branch before it runs. If the merge fails we will stop the pipeline.

Is this what you were after or are you looking for something else?