Update github-trigger-event-options.adoc

[BeFunes]

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[yaningo]

All pipelines triggered by link:https://docs.github.com/en/webhooks/webhook-events-and-payloads#pull_request[pull request events] also have the following xref:variables/#pipeline-values[pipeline values] populated:

[yaningo]

Alternatively:

For all pipelines triggered by link:[https://docs.github.com/en/webhooks/webhook-events-and-payloads#pull_requestpull request events] the following xref:variables/#pipeline-values[pipeline values] are also populated:

[yaningo]

The bullet list is not properly formatted:

[yaningo]

There needs to be an empty line between the sentence "All pipelines triggered by pull request events also have the following pipeline values populated:" and the first item of the list.

And also a full stop at the end of each item.

All pipelines triggered by link:https://docs.github.com/en/webhooks/webhook-events-and-payloads#pull_request[pull request events] also have the following xref:variables/#pipeline-values[pipeline values] are also populated:

* `pipeline.event.github.pull_request.base.ref`: the name of the *base* (or target) branch of the PR - that is the branch that will receive the changes.
* `pipeline.event.github.pull_request.head.ref`: the name of the *head* branch of the PR - that is the branch containing the changes to be merged.
* `pipeline.event.github.pull_request.draft`: a boolean value indicating whether the pull request is a draft.
* `pipeline.event.github.pull_request.title`: the title of the pull request.
* `pipeline.event.github.pull_request.number`: the numeric identifier of the pull request.

These values are extracted directly from the GitHub event payload. The part after prefix `pipeline.event.github.*` matches the corresponding field in the pull request event structure described in link:https://docs.github.com/en/webhooks/webhook-events-and-payloads#pull_request[this page].
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