The old job would trigger the jobs update on a merge request with source
branch "master", e.g. from a fork.

We need to checkout the branch merge-requests/${env.gitlabMergeRequestIid}
in that case.

This code snippet is used in numerous Jenkins pipelines so better
deduplicating it.

SWH migration to GitLab is incoming and we are not using elastic workers
yet in production so we still need to build debian packages for swh modules.

So add support for building the debian packages when pushing tags to swh
module repositories hosted on GitLab.

This job is responsible to setup the webhooks on swh GitLab repositories
enabling to trigger Jenkins builds when pushing changes or creating merge
requests.

It parses Jenkins jobs builder YAML configuration to get the name of the
repos with CI setup and set webhook URLs in GitLab projects through HTTP
requests to the GitLab REST API.

It is triggered at the end of the swh-jenkins-jobs-builder job after jobs
have been reconfigured.

This job is responsible of updating the Jenkins jobs configuration
when executed. It will be triggered when pushing changes to the
swh-jenkins-jobs repository.

When triggered from a GitLab merge request, Jenkins jobs configuration
is not updated, only proper jobs generation is checked.