When I try to apply the last diff in the enclosed file, I get the
following backtrace:

--8<---------------cut here---------------start------------->8---
Debugger entered--Lisp error: (error "End of hunk ambiguously marked")
  signal(error ("End of hunk ambiguously marked"))
  error("End of hunk ambiguously marked")
  diff-sanity-check-hunk()
  diff-find-source-location(nil nil)
  diff-apply-hunk(nil)
  call-interactively(diff-apply-hunk nil nil)
--8<---------------cut here---------------end--------------->8---

Seems to me that diff-mode should be able to handle the output of
git-format-patch; after all, the patch command can.