[filter-repo] How to reorder commits

Elijah:

It seems filter-repo can be used to easily reorder commits, but I'm not able to quite figure out how to do it with callbacks. My goal is:

- keep the cover letter at the start of the series in order to cleanly
  delineate where their work starts (and thus avoid potential problems with
  rebases and finding fork-points with base branches, which tends to give
  newbies trouble)
- when the author is ready to submit their work, move the cover letter to the
  tip of the branch and tag it as "foo-bar-v1"
- when the author is ready to work on their changes, they run --reroll and we
  move the cover letter back to the start of the series, adding any necessary
  template "changes in vX" entries to it

(or maybe it will go completely differently -- it's all very fluid right now)

Basically, is git-filter-repo the right tool to reorder commits, or is it best to go directly with fast-export/fast-import?

Thanks in advance, Konstantin