support running as -osh for use as login shell (#35)

bin/oil.py

@@ -164,7 +164,7 @@ def _ShowVersion():
  print('Platform: %s' % platform.version())


def OshMain(argv):
def OshMain(argv, login_shell):
  spec = args.FlagsAndOptions()
  spec.ShortFlag('-c', args.Str, quit_parsing_flags=True)  # command string
  spec.ShortFlag('-i')  # interactive
@@ -392,8 +392,13 @@ def BoilMain(main_argv):


def OilMain(argv):
  login_shell = False

  b = os.path.basename(argv[0])
  main_name, _ = os.path.splitext(b)
  if main_name.startswith("-"):
    login_shell = True
    main_name = main_name[1:]

  if main_name in ('oil', 'oil_main'):
    try:
@@ -410,12 +415,15 @@ def OilMain(argv):
      sys.exit(0)

    main_name = first_arg
    if main_name.startswith("-"):
      login_shell = True
      main_name = main_name[1:]
    main_argv = argv[2:]
  else:
    main_argv = argv[1:]

  if main_name in ('osh', 'sh'):
    status = OshMain(main_argv)
    status = OshMain(main_argv, login_shell)
    tlog('done osh main')
    return status
  elif main_name == 'wok':