git rebase --committer-date-is-author-date with -i/-p

Hi,

Why doesn't git rebase support --committer-date-is-author-date with
the -i or -p flag?

The only workaround I found so far was to rebase anyway then use `git
filter-branch` to set GIT_COMMITER_DATE to GIT_AUTHOR_DATE for all
commits, but this is far from optimal as it completely loses the
original GIT_COMMITER_DATE.

The use case for this is heavy history rewriting for very ancient
commits, squashing a range of old commits togethers. The commit date
being modified leads to trouble with tools that rely on it.

Is there a better workaround?

Thanks,
Philippe