Subject: How dangerous is --committer-date-is-author-date these days?

From: Johannes Sixt <[email-masked]>
Date: Sat, 28 Sep 2024 08:59:57 +0200

The option --committer-date-is-author-date of git-rebase rewrites the
committer dates like its name suggests. It is not uncommon that commits
are rearranged and cherry-picked. Then, as a consequence, author dates
are not decreasing when walking back in history. Now, if such a history
with a non-monotonic author date is rebased one final time with
--committer-date-is-author-date, this creates a history with
non-monotonic committer dates. I recall that this is not a good thing to
have since it can confuse our history walker.

- Why do we have --committer-date-is-author-date in a porcelain command?
- Should we remove it?
- Should we require an explicit --force instead of implying it?
- Should we issue a big warning about the consequences?

Here is the discussion that introduced the option git-rebase:
rebase -i: support --committer-date-is-author-date
https://lore.kernel.org/git/[email-masked]/

I am asking this here after I have participated in this Stackoverflow
question, where git rebase --committer-date-is-author-date was suggested
as a solution to "rewrite name and email, but not timestamps".
https://stackoverflow.com/questions/79024409

-- Hannes