Log Message:
Updated py-dulwich to 0.17.1.

0.17.1	2017-03-01

 IMPROVEMENTS

 * Add basic 'dulwich pull' command. (Jelmer Vernooij)

 BUG FIXES

 * Cope with existing submodules during pull.
   (Jelmer Vernooij, #505)

0.17.0	2017-03-01

 TEST FIXES

 * Skip test that requires sync to synchronize filesystems if os.sync is
   not available. (Koen Martens)

 IMPROVEMENTS

 * Implement MemoryRepo.{set_description,get_description}.
   (Jelmer Vernooij)

 * Raise exception in Repo.stage() when absolute paths are
   passed in. Allow passing in relative paths to
   porcelain.add().(Jelmer Vernooij)

 BUG FIXES

 * Handle multi-line quoted values in config files.
   (Jelmer Vernooij, #495)

 * Allow porcelain.clone of repository without HEAD.
   (Jelmer Vernooij, #501)

 * Support passing tag ids to Walker()'s include argument.
   (Jelmer Vernooij)

 * Don't strip trailing newlines from extra headers.
   (Nicolas Dandrimont)

 * Set bufsize=0 for subprocess interaction with SSH client.
   Fixes hangs on Python 3. (René Stern, #434)

 * Don't drop first slash for SSH paths, except for those
   starting with "~". (Jelmer Vernooij, René Stern, #463)

 * Properly log off after retrieving just refs.
   (Jelmer Vernooij)