CommentTrigger CI workflow only works on PRs based from the main repo (not forks)

[neuronull]

Noticed in #18337 (comment) , the GHA we use to checkout the branch for the PR when doing a comment trigger, is not handling the case where the PR is coming from a fork off of the main repo.

This appears to be a limitation of https://github.com/xt0rted/pull-request-comment-branch

It would seem that until this is fixed, the comment trigger workflow won't be able to operate on external contributor PRs that are opened from forks of the main repo.

[jszwedko]

@neuronull did you mean to link to an issue on https://github.com/xt0rted/pull-request-comment-branch? If one doesn't exist, could we open one?

[neuronull]

Opened xt0rted/pull-request-comment-branch#385 🙏