Fixing author date and signature when rebasing git commits

When rebasing commits, it's common that the author date gets reset (since you're re-authoring the commit).

Simon Willison's solution using git-filter-repo works, but strips GPG signatures.

To restore the GPG signature, first run the git-filter-repo trick, then run:

$ git \
  -c rebase.instructionFormat='%s%nexec GIT_COMMITTER_DATE="%cD" GIT_AUTHOR_DATE="%aD" git commit --amend --no-edit -S' \
  rebase -f <commit>

I'm sure there's a way to combine the 2.