Distinguish commit vs merge commit in Push Events webhooks payload
maybe change objectKind to "mergePush" ?
As a user that is aiming to integrate an external system with GitLab, I would like to receive a webhook and have GitLab provide to me via the webhook a definitive indicator as to whether or not an action has ever been fired for this given Commit SHA before - or at least know whether or not this commit SHA has been previously committed/merged to this git repo.
This would be functionality [similar to GitHub's](https://developer.github.com/webhooks/event-payloads/#webhook-payload-object-33) `commits[][distinct]` payload field.
## Workaround
__using GitLab API-Created CI Jobs to manage state__
Supposing that I have the ability to perform actions from the external system and that I can store GitLab Personal Access Tokens, I can use the GitLab Commit Status API to
1. [Read to see](https://docs.gitlab.com/ee/api/commits.html#list-the-statuses-of-a-commit) if a given commit has ever received a particular action.
1. If no results are returned for a given job/build name, perform the task in the external system
1. [Create and set the status](https://docs.gitlab.com/ee/api/commits.html#post-the-build-status-to-a-commit) for the given commit and build/job name.
issue