* Investigate files that the programs cannot reproduce. Such files are stored
  in the testsuite git branch.

* Would be nice to keep a md5sums list of the files in the manifest and
  check and error if any are different. The error message from xdelta when
  a source file doesn't have the right checksup is fairly obscure and
  doesn't aid in fixing the problem.

  There's an implementation of this in the manifest-md5sums branch of
  git://git.debian.org/git/users/kibi-guest/pristine-tar.git , but I have
  not yet decided about applying it, since it would bloat the delta files
  with a list of all the files and md5sums..

* Optimisation: Enhance zgz so it runs multiple compression alternatives
  block-by-block in parallell, aborting compressors when they differ
  from the target file.

* Add binary deltas for unreproducible bz2 files. (But currently, only two
  bz2 files are known that fails to reproduce: nsis and freecol in testsuite.)

* Support checkout/checkin using other VCS than git.

  bzr-builddeb stores pristine-tar data in bzr repositories.
  The delta is stored in a bzr revprop named "deb-pristine-delta"
  or "deb-pristine-delta-bz2".