message: fbcode_builder: getdeps: add clean command
  Summary:
  This cleans up the scratch dir, removing everything except
  for downloaded tarballs.
diff: @@ -112,17 +112,28 @@ class ListDepsCmd(SubCmd):
  )
  -@cmd("build", "build a given project")
  -class BuildCmd(SubCmd):
  - def run(self, args):
  - opts = setup_build_options(args)
  - if args.clean:
  +def clean_dirs(opts):
  for d in ["build", "installed", "extracted", "shipit"]:
  d = os.path.join(opts.scratch_dir, d)
  print("Cleaning %s..." % d)
  if os.path.exists(d):
  shutil.rmtree(d)
  +
  +@cmd("clean", "clean up the scratch dir")
  +class CleanCmd(SubCmd):
  + def run(self, args):
  + opts = setup_build_options(args)
  + clean_dirs(opts)
  +
  +
  +@cmd("build", "build a given project")
  +class BuildCmd(SubCmd):
  + def run(self, args):
  + opts = setup_build_options(args)
  + if args.clean:
  + clean_dirs(opts)
  +
  manifest = load_project(opts, args.project)
  ctx = context_from_host_tuple()
  