chromium的部署工具depot_tools和gclient

depot_tools是个工具包，里面包含gclient、gcl、gn和ninja等工具。其中gclient是代码获取工具，它其实是利用了svn和git。主要涉及的depot_tools文件夹下的文件有：gclient、gclient.py、subcommand.py、gclient_utils.py。

gclient文件是个bash脚本:

#########glcient###########/usr/bin/bash base_dir=$(dirname "$0")  if [[ "#grep#fetch#cleanup#diff#" != *"#$1#"* ]]; then   "$base_dir"/update_depot_tools fi  PYTHONDONTWRITEBYTECODE=1 exec python "$base_dir/gclient.py" "$@"

首先，获取脚本的目录并赋值给base_dir，然后判断命令参数1是否为grep|fetch|cleanup|diff，如不是则执行base_dir下的updat_depot_tools脚本，该脚本更新git、svn工具。最后调用当前脚本目录(depot_tools)下的python脚本gclient.py，并把参数都传递给该脚本。

###############glcient.py######## 文件最后def Main(argv):      .....   dispatcher = subcommand.CommandDispatcher(__name__)   try:     return dispatcher.execute(OptionParser(), argv)    ......if '__main__' == __name__:   sys.exit(Main(sys.argv[1:]))

在gclient.py脚本开始，调用函数Main，参数为bash脚本传递来的。Main主要执行两个过程，一是建立dispatcher对象，参数为当前模块；然后调用dispatcher的execute方法，参数一是OptionParser对象，参数二为传递给Main的参数。

下面进入subcommand模块下的类CommandDispatcher，分析execute方法。

################# subcommand.py ###########class CommandDispatcher(object):  def __init__(self, module):    """module is the name of the main python module where to look for commands.    The python builtin variable __name__ MUST be used for |module|. If the    script is executed in the form 'python script.py', __name__ == '__main__'    and sys.modules['script'] doesn't exist. On the other hand if it is unit    tested, __main__ will be the unit test's module so it has to reference to    itself with 'script'. __name__ always match the right value.    """    self.module = sys.modules[module]  def enumerate_commands(self):    """Returns a dict of command and their handling function.    The commands must be in the '__main__' modules. To import a command from a    submodule, use:      from mysubcommand import CMDfoo    Automatically adds 'help' if not already defined.    A command can be effectively disabled by defining a global variable to None,    e.g.:      CMDhelp = None    """    cmds = dict(        (fn[3:], getattr(self.module, fn))        for fn in dir(self.module) if fn.startswith('CMD'))    cmds.setdefault('help', CMDhelp)    return cmds  def find_nearest_command(self, name):    """Retrieves the function to handle a command.    It automatically tries to guess the intended command by handling typos or    incomplete names.    """    # Implicitly replace foo-bar to foo_bar since foo-bar is not a valid python    # symbol but it's faster to type.    name = name.replace('-', '_')    commands = self.enumerate_commands()    if name in commands:      return commands[name]    # An exact match was not found. Try to be smart and look if there's    # something similar.    commands_with_prefix = [c for c in commands if c.startswith(name)]    if len(commands_with_prefix) == 1:      return commands[commands_with_prefix[0]]    # A #closeenough approximation of levenshtein distance.    def close_enough(a, b):      return difflib.SequenceMatcher(a=a, b=b).ratio()    hamming_commands = sorted(        ((close_enough(c, name), c) for c in commands),        reverse=True)    if (hamming_commands[0][0] - hamming_commands[1][0]) < 0.3:      # Too ambiguous.      return    if hamming_commands[0][0] < 0.8:      # Not similar enough. Don't be a fool and run a random command.      return    return commands[hamming_commands[0][1]]  def _gen_commands_list(self):    """Generates the short list of supported commands."""    commands = self.enumerate_commands()    docs = sorted(        (name, self._create_command_summary(name, handler))        for name, handler in commands.iteritems())    # Skip commands without a docstring.    docs = [i for i in docs if i[1]]    # Then calculate maximum length for alignment:    length = max(len(c) for c in commands)    # Look if color is supported.    colors = _get_color_module()    green = reset = ''    if colors:      green = colors.Fore.GREEN      reset = colors.Fore.RESET    return (        'Commands are:\n' +        ''.join(            '  %s%-*s%s %s\n' % (green, length, name, reset, doc)            for name, doc in docs))  def _add_command_usage(self, parser, command):    """Modifies an OptionParser object with the function's documentation."""    name = command.__name__[3:]    if name == 'help':      name = '<command>'      # Use the module's docstring as the description for the 'help' command if      # available.      parser.description = (self.module.__doc__ or '').rstrip()      if parser.description:        parser.description += '\n\n'      parser.description += self._gen_commands_list()      # Do not touch epilog.    else:      # Use the command's docstring if available. For commands, unlike module      # docstring, realign.      lines = (command.__doc__ or '').rstrip().splitlines()      if lines[:1]:        rest = textwrap.dedent('\n'.join(lines[1:]))        parser.description = '\n'.join((lines[0], rest))      else:        parser.description = lines[0]      if parser.description:        parser.description += '\n'      parser.epilog = getattr(command, 'epilog', None)      if parser.epilog:        parser.epilog = '\n' + parser.epilog.strip() + '\n'    more = getattr(command, 'usage_more', '')    parser.set_usage(        'usage: %%prog %s [options]%s' % (name, '' if not more else ' ' + more))  @staticmethod  def _create_command_summary(name, command):    """Creates a oneline summary from the command's docstring."""    if name != command.__name__[3:]:      # Skip aliases.      return ''    doc = command.__doc__ or ''    line = doc.split('\n', 1)[0].rstrip('.')    if not line:      return line    return (line[0].lower() + line[1:]).strip()  def execute(self, parser, args):    """Dispatches execution to the right command.    Fallbacks to 'help' if not disabled.    """    # Unconditionally disable format_description() and format_epilog().    # Technically, a formatter should be used but it's not worth (yet) the    # trouble.    parser.format_description = lambda _: parser.description or ''    parser.format_epilog = lambda _: parser.epilog or ''    if args:      if args[0] in ('-h', '--help') and len(args) > 1:        # Inverse the argument order so 'tool --help cmd' is rewritten to        # 'tool cmd --help'.        args = [args[1], args[0]] + args[2:]      command = self.find_nearest_command(args[0])      if command:        if command.__name__ == 'CMDhelp' and len(args) > 1:          # Inverse the arguments order so 'tool help cmd' is rewritten to          # 'tool cmd --help'. Do it here since we want 'tool hel cmd' to work          # too.          args = [args[1], '--help'] + args[2:]          command = self.find_nearest_command(args[0]) or command        # "fix" the usage and the description now that we know the subcommand.        self._add_command_usage(parser, command)        return command(parser, args[1:])    cmdhelp = self.enumerate_commands().get('help')    if cmdhelp:      # Not a known command. Default to help.      self._add_command_usage(parser, cmdhelp)      return cmdhelp(parser, args)    # Nothing can be done.    return 2

在gcient.py中，dispatcher = subcomamnd.CommandDispatcher(__name__)，可以看出传入的参数是gclient.py这个模块。在CommandDispatcher的__init__中，self.module就是gclent。了解这点对理解后面的enumrate_commands函数有用。从它的名字就可以看出是枚举所有支持的命令，返回的结果是dict，键是命令名称，值为对应的处理函数，如{"sync" : CMDsync}。其他函数如_add_command_usage, _create_command_summary, _gen_commands_list是些辅助函数，功能也比较明确。比较复杂的是find_nearest_command，它是从enumerate_commands生成的dict字典里查找命令，如果没有精确匹配的，就通过模糊查找，并返回对应命令的处理函数。

############# gclient.py ##################class OptionParser(optparse.OptionParser):  gclientfile_default = os.environ.get('GCLIENT_FILE', '.gclient')  def __init__(self, **kwargs):    optparse.OptionParser.__init__(        self, version='%prog ' + __version__, **kwargs)    # Some arm boards have issues with parallel sync.    if platform.machine().startswith('arm'):      jobs = 1    else:      jobs = max(8, gclient_utils.NumLocalCpus())    # cmp: 2013/06/19    # Temporary workaround to lower bot-load on SVN server.    # Bypassed if a bot_update flag is detected.    if (os.environ.get('CHROME_HEADLESS') == '1' and        not os.path.exists('update.flag')):      jobs = 1    self.add_option(        '-j', '--jobs', default=jobs, type='int',        help='Specify how many SCM commands can run in parallel; defaults to '             '%default on this machine')    self.add_option(        '-v', '--verbose', action='count', default=0,        help='Produces additional output for diagnostics. Can be used up to '             'three times for more logging info.')    self.add_option(        '--gclientfile', dest='config_filename',        help='Specify an alternate %s file' % self.gclientfile_default)    self.add_option(        '--spec',        help='create a gclient file containing the provided string. Due to '            'Cygwin/Python brokenness, it can\'t contain any newlines.')    self.add_option(        '--no-nag-max', default=False, action='store_true',        help='Ignored for backwards compatibility.')

参数OptionParser是gclient.py中的一个类，它继承子模块的optparser.OptionParser。主要功能是解析参数，并返回tuple（options， args），关于OptionParser这个例子说明的很清楚。返回值就是输入参数被格式化分析后的结果。这个函数处理分两个层面，一是如果是帮助查询，一个是执行命令。在帮助查询时，用户输入的命令如：gclient --help sync等。其实，传到execute的时候，参数变成--help sync，那么首先是调换参数位置，使得结果为sync --help，也就是args[0]为"sync", args[1]为--help，然后调用self.fine_nearest_command函数，查找精确命令或者最相似的模糊匹配的命令，并把结果（命令处理函数以CMD开头）赋值给command变量。

进入到execute()，解析参数，find_nearest_commands()得到命令后，判断是不是帮助命令，如果不是就直接调用对应的处理函数return command(parser, args[1:])。用上例来说就是调用CMDsync函数，参数是parser 和sync后的参数。

看看CMDsync是如何处理输入参数的？

#############gclient.py#############def CMDsync(parser, args):  """Checkout/update all modules."""  parser.add_option('-f', '--force', action='store_true',                    help='force update even for unchanged modules')  parser.add_option('-n', '--nohooks', action='store_true',                    help='don\'t run hooks after the update is complete')  parser.add_option('-p', '--noprehooks', action='store_true',                    help='don\'t run pre-DEPS hooks', default=False)  parser.add_option('-r', '--revision', action='append',                    dest='revisions', metavar='REV', default=[],                    help='Enforces revision/hash for the solutions with the '                         'format src@rev. The src@ part is optional and can be '                         'skipped. -r can be used multiple times when .gclient '                         'has multiple solutions configured and will work even '                         'if the src@ part is skipped. Note that specifying '                         '--revision means your safesync_url gets ignored.')  parser.add_option('--with_branch_heads', action='store_true',                    help='Clone git "branch_heads" refspecs in addition to '                         'the default refspecs. This adds about 1/2GB to a '                         'full checkout. (git only)')  parser.add_option('-t', '--transitive', action='store_true',                    help='When a revision is specified (in the DEPS file or '                          'with the command-line flag), transitively update '                          'the dependencies to the date of the given revision. '                          'Only supported for SVN repositories.')  parser.add_option('-H', '--head', action='store_true',                    help='skips any safesync_urls specified in '                         'configured solutions and sync to head instead')  parser.add_option('-D', '--delete_unversioned_trees', action='store_true',                    help='Deletes from the working copy any dependencies that '                         'have been removed since the last sync, as long as '                         'there are no local modifications. When used with '                         '--force, such dependencies are removed even if they '                         'have local modifications. When used with --reset, '                         'all untracked directories are removed from the '                         'working copy, excluding those which are explicitly '                         'ignored in the repository.')  parser.add_option('-R', '--reset', action='store_true',                    help='resets any local changes before updating (git only)')  parser.add_option('-M', '--merge', action='store_true',                    help='merge upstream changes instead of trying to '                         'fast-forward or rebase')  parser.add_option('--deps', dest='deps_os', metavar='OS_LIST',                    help='override deps for the specified (comma-separated) '                         'platform(s); \'all\' will process all deps_os '                         'references')  parser.add_option('-m', '--manually_grab_svn_rev', action='store_true',                    help='Skip svn up whenever possible by requesting '                         'actual HEAD revision from the repository')  parser.add_option('--upstream', action='store_true',                    help='Make repo state match upstream branch.')  parser.add_option('--output-json',                    help='Output a json document to this path containing '                         'summary information about the sync.')  (options, args) = parser.parse_args(args)  client = GClient.LoadCurrentConfig(options)  if not client:    raise gclient_utils.Error('client not configured; see \'gclient config\'')  if options.revisions and options.head:    # TODO(maruel): Make it a parser.error if it doesn't break any builder.    print('Warning: you cannot use both --head and --revision')  if options.verbose:    # Print out the .gclient file.  This is longer than if we just printed the    # client dict, but more legible, and it might contain helpful comments.    print(client.config_content)  ret = client.RunOnDeps('update', args)  if options.output_json:    slns = {}    for d in client.subtree(True):      normed = d.name.replace('\\', '/').rstrip('/') + '/'      slns[normed] = {          'revision': d.got_revision,          'scm': d.used_scm.name if d.used_scm else None,      }    with open(options.output_json, 'wb') as f:      json.dump({'solutions': slns}, f)  return retCMDupdate = CMDsync

通过options，args = parser.parse_args(args)，得到对CMDsync命令参数的解析，然后调用Gclient.LoadCurrentConfig(options)，为简单起见，我们输入的是gclient sync，那么options和args为空。

############glcient.py#############def LoadCurrentConfig(options):    """Searches for and loads a .gclient file relative to the current working    dir. Returns a GClient object."""    if options.spec:      client = GClient('.', options)      client.SetConfig(options.spec)    else:      path = gclient_utils.FindGclientRoot(os.getcwd(), options.config_filename)      if not path:        return None      client = GClient(path, options)      client.SetConfig(gclient_utils.FileRead(          os.path.join(path, options.config_filename)))    if (options.revisions and        len(client.dependencies) > 1 and        any('@' not in r for r in options.revisions)):      print >> sys.stderr, (          'You must specify the full solution name like --revision %s@%s\n'          'when you have multiple solutions setup in your .gclient file.\n'          'Other solutions present are: %s.') % (              client.dependencies[0].name,              options.revisions[0],              ', '.join(s.name for s in client.dependencies[1:]))    return client

该函数查询当前目录下.glcient文件，最终返回client对象。该函数会调用到GClient(path, options):

############## gclient.py ##################class GClient(Dependency):  """Object that represent a gclient checkout. A tree of Dependency(), one per  solution or DEPS entry."""  DEPS_OS_CHOICES = {    "win32": "win",    "win": "win",    "cygwin": "win",    "darwin": "mac",    "mac": "mac",    "unix": "unix",    "linux": "unix",    "linux2": "unix",    "linux3": "unix",    "android": "android",  }  DEFAULT_CLIENT_FILE_TEXT = ("""\solutions = [  { "name"        : "%(solution_name)s",    "url"         : "%(solution_url)s",    "deps_file"   : "%(deps_file)s",    "managed"     : %(managed)s,    "custom_deps" : {    },    "safesync_url": "%(safesync_url)s",  },]cache_dir = %(cache_dir)r""")  DEFAULT_SNAPSHOT_SOLUTION_TEXT = ("""\  { "name"        : "%(solution_name)s",    "url"         : "%(solution_url)s",    "deps_file"   : "%(deps_file)s",    "managed"     : %(managed)s,    "custom_deps" : {%(solution_deps)s    },    "safesync_url": "%(safesync_url)s",  },""")  DEFAULT_SNAPSHOT_FILE_TEXT = ("""\# Snapshot generated with gclient revinfo --snapshotsolutions = [%(solution_list)s]""")  def __init__(self, root_dir, options):    # Do not change previous behavior. Only solution level and immediate DEPS    # are processed.    self._recursion_limit = 2    Dependency.__init__(self, None, None, None, None, True, None, None, None,                        'unused', True)    self._options = options    if options.deps_os:      enforced_os = options.deps_os.split(',')    else:      enforced_os = [self.DEPS_OS_CHOICES.get(sys.platform, 'unix')]    if 'all' in enforced_os:      enforced_os = self.DEPS_OS_CHOICES.itervalues()    self._enforced_os = tuple(set(enforced_os))    self._root_dir = root_dir    self.config_content = None  def SetConfig(self, content):    assert not self.dependencies    config_dict = {}    self.config_content = content    try:      exec(content, config_dict)    except SyntaxError, e:      gclient_utils.SyntaxErrorToError('.gclient', e)    # Append any target OS that is not already being enforced to the tuple.    target_os = config_dict.get('target_os', [])    if config_dict.get('target_os_only', False):      self._enforced_os = tuple(set(target_os))    else:      self._enforced_os = tuple(set(self._enforced_os).union(target_os))    gclient_scm.GitWrapper.cache_dir = config_dict.get('cache_dir')    if not target_os and config_dict.get('target_os_only', False):      raise gclient_utils.Error('Can\'t use target_os_only if target_os is '                                'not specified')    deps_to_add = []    for s in config_dict.get('solutions', []):      try:        deps_to_add.append(Dependency(            self, s['name'], s['url'],            s.get('safesync_url', None),            s.get('managed', True),            s.get('custom_deps', {}),            s.get('custom_vars', {}),            s.get('custom_hooks', []),            s.get('deps_file', 'DEPS'),            True))      except KeyError:        raise gclient_utils.Error('Invalid .gclient file. Solution is '                                  'incomplete: %s' % s)    self.add_dependencies_and_close(deps_to_add, config_dict.get('hooks', []))    logging.info('SetConfig() done')  def SaveConfig(self):    gclient_utils.FileWrite(os.path.join(self.root_dir,                                         self._options.config_filename),                            self.config_content)        def RunOnDeps(self, command, args, ignore_requirements=False, progress=True):    """Runs a command on each dependency in a client and its dependencies.    Args:      command: The command to use (e.g., 'status' or 'diff')      args: list of str - extra arguments to add to the command line.    """    if not self.dependencies:      raise gclient_utils.Error('No solution specified')    revision_overrides = {}    # It's unnecessary to check for revision overrides for 'recurse'.    # Save a few seconds by not calling _EnforceRevisions() in that case.    if command not in ('diff', 'recurse', 'runhooks', 'status'):      revision_overrides = self._EnforceRevisions()    pm = None    # Disable progress for non-tty stdout.    if (sys.stdout.isatty() and not self._options.verbose and progress):      if command in ('update', 'revert'):        pm = Progress('Syncing projects', 1)      elif command == 'recurse':        pm = Progress(' '.join(args), 1)    work_queue = gclient_utils.ExecutionQueue(        self._options.jobs, pm, ignore_requirements=ignore_requirements)    for s in self.dependencies:      work_queue.enqueue(s)    work_queue.flush(revision_overrides, command, args, options=self._options)    # Once all the dependencies have been processed, it's now safe to run the    # hooks.    if not self._options.nohooks:      self.RunHooksRecursively(self._options)    if command == 'update':      # Notify the user if there is an orphaned entry in their working copy.      # Only delete the directory if there are no changes in it, and      # delete_unversioned_trees is set to true.      entries = [i.name for i in self.root.subtree(False) if i.url]      full_entries = [os.path.join(self.root_dir, e.replace('/', os.path.sep))                      for e in entries]      for entry, prev_url in self._ReadEntries().iteritems():        if not prev_url:          # entry must have been overridden via .gclient custom_deps          continue        # Fix path separator on Windows.        entry_fixed = entry.replace('/', os.path.sep)        e_dir = os.path.join(self.root_dir, entry_fixed)        def _IsParentOfAny(parent, path_list):          parent_plus_slash = parent + '/'          return any(              path[:len(parent_plus_slash)] == parent_plus_slash              for path in path_list)        # Use entry and not entry_fixed there.        if (entry not in entries and            (not any(path.startswith(entry + '/') for path in entries)) and            os.path.exists(e_dir)):          scm = gclient_scm.CreateSCM(prev_url, self.root_dir, entry_fixed)          # Check to see if this directory is now part of a higher-up checkout.          if scm.GetCheckoutRoot() in full_entries:            logging.info('%s is part of a higher level checkout, not '                         'removing.', scm.GetCheckoutRoot())            continue          file_list = []          scm.status(self._options, [], file_list)          modified_files = file_list != []          if (not self._options.delete_unversioned_trees or              (modified_files and not self._options.force)):            # There are modified files in this entry. Keep warning until            # removed.            print(('\nWARNING: \'%s\' is no longer part of this client.  '                   'It is recommended that you manually remove it.\n') %                      entry_fixed)          else:            # Delete the entry            print('\n________ deleting \'%s\' in \'%s\'' % (                entry_fixed, self.root_dir))            gclient_utils.rmtree(e_dir)      # record the current list of entries for next time      self._SaveEntries()    return 0 

client.SetConfig()读取配置文件里的solutions，构建dependencies的list变量deps_to_add，然后调用.add_dependencies_and_close，参数就是包含deps_to_add。在add_dependencies_and_close函数里验证deps，如果是有效的，就加入到依赖树中。

在CMDsync函数里，执行client.RunOnDeps()。它将dependengcies的每个任务加入到gclient_tuils.ExecutionQueue队列并执行。完成所有任务后执行runhook。

######## src/DEPS #############hooks = [  {    # A change to a .gyp, .gypi, or to GYP itself should run the generator.    "pattern": ".",    "action": ["python", "src/build/gyp_chromium"],  },]

上面是src下的DEPS关于hooks的部分，也就是执行完sync命令后，文件更新就执行src/build/gyp_chromium文件。