When running git-webkit pr on a branch belonging to a non-origin remote, we should rebase against the non-origin remote's record of the target branch.
<rdar://problem/96851195>
Pull request: https://github.com/WebKit/WebKit/pull/2311
Committed 252390@main (c286bc3a89ff): <https://commits.webkit.org/252390@main> Reviewed commits have been landed. Closing PR #2311 and removing active labels.
Re-opened since this is blocked by bug 242656
Bug reopened to test automated revert tooling