title: git rebase --committer-date-is-author-date --root does not work
body: <p>I try to set the committer date of the latest commit to its author date. Usually this works with <code>git rebase --committer-date-is-author-date HEAD~1</code>. Unfortunately there is only one commit which means that I have to use <code>--root</code> instead of <code>HEAD~1</code> but <code>git rebase --committer-date-is-author-date --root</code> does not set the committer date to the author date for some reason. What can I do?</p>