While 'git commit --amend' works, that's only because we hard-code HEAD in our prepare-commit-msg hook. We should instead use the argument 'git commit' is providing us.
<rdar://problem/107729416>
Pull request: https://github.com/WebKit/WebKit/pull/12480
Committed 262688@main (ba739f2564d7): <https://commits.webkit.org/262688@main> Reviewed commits have been landed. Closing PR #12480 and removing active labels.