Merge branch 'fc/fast-export-fixes'

Merge branch 'fc/fast-export-fixes'

Various updates to fast-export used in the context of the remote
helper interface.

* fc/fast-export-fixes:
  fast-export: make sure updated refs get updated
  fast-export: don't handle uninteresting refs
  fast-export: fix comparison in tests
  fast-export: trivial cleanup
  remote-testgit: implement the "done" feature manually
  remote-testgit: report success after an import
  remote-testgit: exercise more features
  remote-testgit: cleanup tests
  remote-testgit: remove irrelevant test
  remote-testgit: remove non-local functionality
  Add new simplified git-remote-testgit
  Rename git-remote-testgit to git-remote-testpy
  remote-helpers: fix failure message
  remote-testgit: fix direction of marks
  fast-export: avoid importing blob marks