multibranch pipeline github scm context

[Arvind Jayaprakash]

I'd like find out the following things from a multibranch pipeline script associated with a github scm provider

• Is this build happening for a branch or a pull request?
• If it is for a pull request, then I need to know these as well
• Commit-id of the tip of pull request
• Commit-id of the merge target
• Which branch is the destination for merging the pull request?
• Is the pull request originating from a forked repo or branch on the same repo?

Would it be possible to find all of these from the scm variable? If so how?

PS: complete documentation on what the scm variable contains would be useful