[DO NOT MERGE] test PR: changes in vNext but not vCurrent, in a forked PR

[pepopowitz]

Description

This PR exists as a test case, and will be deleted after #3091 is completed.

Scenario: changes are made in vNext but not vCurrent, in a forked PR.

Expected result: a comment suggesting changes in vNext be ported to vCurrent.

When should this change go live?

Never!

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[pepopowitz]

Ok, this just doesn't work in a forked PR.

The checkout action, because it's running on pull_request_target, is checking out the host's SHA, which is what this is merging into. So it's not running the action with the changes in this PR.

See this conversation for a long discussion of what might be the right thing to check out on pull_request_target.

For now I'm going to revert #3091 to triggering on pull_request instead of pull_request_target, and exclude forked PRs from my acceptance criteria. I'll try to fix forked PRs in a follow-up.