Include branch name in Merge Request Webhook Event

Problem to solve

When a pipeline event is created from a merge request the payload no longer includes the specifics branch name. it appears this is a result of the changes made to merge requests here:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25504

Currently Payload Example:

{
	"object_kind": "pipeline",
	"object_attributes": {
		"id": 5,
		"ref": "refs/merge-requests/15/head",

Prior payload example:

{
	"object_kind": "pipeline",
	"object_attributes": {
		"id": 5,
		"ref": "branch-name",

Proposal

Include the branch name as a property in the payload.

{
   "object_kind": "pipeline",
   "object_attributes":{
      "id": 5,
      "ref": "refs/merge-requests/15/head",
      "branch": "branch-name"

Documentation

https://docs.gitlab.com/ee/user/project/integrations/webhooks.html#pipeline-events

{
   "object_kind": "pipeline",
   "object_attributes":{
      "id": 31,
      "ref": "master",

https://docs.gitlab.com/ee/ci/merge_request_pipelines/

Note: As of GitLab 11.10, pipelines for merge requests require GitLab Runner 11.9 or higher due to the recent refspecs changes. Anything lower will cause the pipeline to fail.

Links / references

Internal ZD