* Send all debug and verbose prints to stderr, reserving stdout for

* Send all debug and verbose prints to stderr, reserving stdout for
  outputting deltas etc.
* pristine-tar commit was not generating deltas against the specified
  upstream branch, but against the unpacked contents of the source tarball.
  Fix it to use the upstream branch, ensuring that no matter what branch is
  given, the delta that is created can always recreate the source tarball.