Most real breakage comes from nuking the custom Printer:
- patch formatting is probably pretty broken: we now use Text for Doc, which
  means Doc is no longer a good way to format non-text (i.e. hunk, which is
  bytes) data
- no colorful printing of stuff

What got replaced, by what:
- Printer -> wl-pprint-text
- hashed-storage -> fslib
- Darcs.Patch.FileName -> pathlib

Other incompatible (API) changes:
- Data.Patch.Info has a completely new API
- patch2patchinfo -> patchinfo

Things to consider:
- mv = demanifest ; manifest (getting rid of a Move patch type)
  late commute failures? (and, is this a problem?)
  - (even for idempotent manifest):
    manifest Y dir new :> (demanifest X dir old; manifest X dir new)
    (demanifest X dir old; manifest X dir new) :> demanifest Y dir old
  - requires multiple manifestations