[cctest] adding --help option to output basic information about cctest

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 153 matching lines @@
               "mipsel",
               "mips64el",
               "nacl_ia32",
               "nacl_x64",
               "x87",
               "arm64"]
 
 
 def BuildOptions():
   result = optparse.OptionParser()
+  result.usage = '%prog [options] [tests]'
+  result.description = """TESTS: %s""" % (DEFAULT_TESTS)
   result.add_option("--arch",
                     help=("The architecture to run tests for, "
-                          "'auto' or 'native' for auto-detect"),
+                          "'auto' or 'native' for auto-detect: %s" % SUPPORTED_ARCHS),
                     default="ia32,x64,arm")
   result.add_option("--arch-and-mode",
                     help="Architecture and mode in the format 'arch.mode'",
                     default=None)
   result.add_option("--asan",
                     help="Regard test expectations for ASAN",
                     default=False, action="store_true")
   result.add_option("--buildbot",
                     help="Adapt to path structure used on buildbots",
                     default=False, action="store_true")
@@ skipping 26 matching lines @@
                     help="Download missing test suite data and exit",
                     default=False, action="store_true")
   result.add_option("--extra-flags",
                     help="Additional flags to pass to each test command",
                     default="")
   result.add_option("--isolates", help="Whether to test isolates",
                     default=False, action="store_true")
   result.add_option("-j", help="The number of parallel tasks to run",
                     default=0, type="int")
   result.add_option("-m", "--mode",
-                    help="The test modes in which to run (comma-separated)",
+                    help="The test modes in which to run (comma-separated,"
+                    " uppercase for ninja and buildbot builds): %s" % MODES.keys(),
                     default="release,debug")
   result.add_option("--no-harness", "--noharness",
                     help="Run without test harness of a given suite",
                     default=False, action="store_true")
   result.add_option("--no-i18n", "--noi18n",
                     help="Skip internationalization tests",
                     default=False, action="store_true")
   result.add_option("--no-network", "--nonetwork",
                     help="Don't distribute tests on the network",
                     default=(utils.GuessOS() != "linux"),
                     dest="no_network", action="store_true")
   result.add_option("--no-presubmit", "--nopresubmit",
                     help='Skip presubmit checks',
                     default=False, dest="no_presubmit", action="store_true")
   result.add_option("--no-snap", "--nosnap",
                     help='Test a build compiled without snapshot.',
                     default=False, dest="no_snap", action="store_true")
   result.add_option("--no-sorting", "--nosorting",
                     help="Don't sort tests according to duration of last run.",
                     default=False, dest="no_sorting", action="store_true")
   result.add_option("--no-stress", "--nostress",
                     help="Don't run crankshaft --always-opt --stress-op test",
                     default=False, dest="no_stress", action="store_true")
   result.add_option("--no-variants", "--novariants",
                     help="Don't run any testing variants",
                     default=False, dest="no_variants", action="store_true")
   result.add_option("--variants",
-                    help="Comma-separated list of testing variants")
+                    help="Comma-separated list of testing variants: %s" % VARIANTS)
   result.add_option("--outdir", help="Base directory with compile output",
                     default="out")
   result.add_option("--predictable",
                     help="Compare output of several reruns of each test",
                     default=False, action="store_true")
   result.add_option("-p", "--progress",
                     help=("The style of progress indicator"
                           " (verbose, dots, color, mono)"),
                     choices=progress.PROGRESS_INDICATORS.keys(), default="mono")
   result.add_option("--quickcheck", default=False, action="store_true",
@@ skipping 279 matching lines @@
       # buildbot. Currently this is capitalized Release and Debug.
       shell_dir = os.path.join(workspace, options.outdir, mode)
       mode = BuildbotToV8Mode(mode)
     else:
       shell_dir = os.path.join(
           workspace,
           options.outdir,
           "%s.%s" % (arch, MODES[mode]["output_folder"]),
       )
   shell_dir = os.path.relpath(shell_dir)
+  if not os.path.exists(shell_dir):
+      raise Exception('Could not find shell_dir: "%s"' % shell_dir)
 
   # Populate context object.
   mode_flags = MODES[mode]["flags"]
   timeout = options.timeout
   if timeout == -1:
     # Simulators are slow, therefore allow a longer default timeout.
     if arch in SLOW_ARCHS:
       timeout = 2 * TIMEOUT_DEFAULT;
     else:
       timeout = TIMEOUT_DEFAULT;
@@ skipping 139 matching lines @@
     verbose.PrintTestDurations(suites, overall_duration)
 
   if num_tests == 0:
     print("Warning: no tests were run!")
 
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())