阅读repo脚本

repo篇幅比较长，但是结构很清晰 记得我们在repo下载代码的时候，经常会出现一些错误，那时我们往往手足无措，可是当我们花点时间分析了repo，发现错误输出的错误往往能够找到真正的原因，因为对目前python不是很熟，只能尽力分析了，同样的，我们在git操作时候，也经常出一些错误，下次会针对常见的git 操作的错误信息进行源码分析

#!/bin/sh

## repo default configuration

## repo采用的是python语法，通篇也不难，我们慢慢分析

REPO_URL='ssh://username@61.143.53.198/git_repo/repo.git' #变量赋值，指明下载的SSH协议和具体路径

REPO_REV='master'

# Copyright (C) 2008 Google Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

magic='--calling-python-from-/bin/sh--'

"""exec" python -E "$0" "$@" """#$magic"  #巧妙的通过python三引号字串写出了一个能被python和shell script都能理解的代码，以此为界，代码由 Shell 脚本进入了 Python 的世界，这里起名为“魔法”名符其实

if __name__ == '__main__':  #可以理解为"if __name__=="__main__":" 这一句与c中的main()函数所表述的是一致的，即作为入口

  import sys

  if sys.argv[-1] == '#%s' % magic:

    del sys.argv[-1]

del magic

# increment this whenever we make important changes to this script

VERSION = (1, 13)

# increment this if the MAINTAINER_KEYS block is modified

KEYRING_VERSION = (1,0)

MAINTAINER_KEYS = """

     Repo Maintainer <[e-mail]>

-----BEGIN PGP PUBLIC KEY BLOCK-----

Version: GnuPG v1.4.2.2 (GNU/Linux)

mQGiBEj3ugERBACrLJh/ZPyVSKeClMuznFIrsQ+hpNnmJGw1a9GXKYKk8qHPhAZf

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VCkk1l8qqLiuW0fo+ZkPY5qOgrvc0HW1SmdH649uNwqCbcKb6CxaTxzhOwCgj3AP

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ouWxX1faR+vU3b+Y2/DGjtXQMzG0qpetaTHC/AxxHpgt/dCkWI6ljYDnxgPLwG0a

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HTHs37+/QLMomGEGKZMWi0dShU2J5mNRQu3Hhxl3hHDVbt5CeJBb26aQcQrFz69W

zE3GNvmJosh6leayjtI9P2A6iEkEGBECAAkFAkj3uiACGwwACgkQFlMNXpIPXGWp

TACbBS+Up3RpfYVfd63c1cDdlru13pQAn3NQy/SN858MkxN+zym86UBgOad2

=CMiZ

-----END PGP PUBLIC KEY BLOCK-----

"""

GIT = 'git' # our git command

MIN_GIT_VERSION = (1, 5, 4) # minimum supported git version

repodir = '.repo' # name of repo's private directory

S_repo = 'repo' # special repo reposiory

S_manifests = 'manifests' # special manifest repository

REPO_MAIN = S_repo + '/main.py' # main script

import optparse

import os

import re

import readline

import subprocess

import sys

import urllib2

home_dot_repo = os.path.expanduser('~/.repoconfig')  #返回波浪号~的绝对路径，如果你的当前用户是user的话,返回的便是/home/user/.repoconfig

gpg_dir = os.path.join(home_dot_repo, 'gnupg') #将 home_dot_repo这个变量和'gnupg'连接起来，返回的路径是/home/user/.repoconfig/gnupg

extra_args = [] #定义参数数组

init_optparse = optparse.OptionParser(usage="repo init -u url [options]")  # optparse是专门用来在命令行添加选项的一个模块 很显然，这是再添加一个usage

# Logging

group = init_optparse.add_option_group('Logging options')  # 增加Logging options这一项帮助信息

group.add_option('-q', '--quiet',

                 dest="quiet", action="store_true", default=False,

                 help="be quiet")

# Manifest # 增加Manifest options这一项的帮助信息

group = init_optparse.add_option_group('Manifest options')

group.add_option('-u', '--manifest-url',

                 dest='manifest_url',

                 help='manifest repository location', metavar='URL')

group.add_option('-b', '--manifest-branch',

                 dest='manifest_branch',

                 help='manifest branch or revision', metavar='REVISION')

group.add_option('-m', '--manifest-name',

                 dest='manifest_name',

                 help='initial manifest file', metavar='NAME.xml')

group.add_option('--mirror',

                 dest='mirror', action='store_true',

                 help='mirror the forrest')

group.add_option('--reference',

                 dest='reference',

                 help='location of mirror directory', metavar='DIR')

group.add_option('--depth', type='int', default=None,

                 dest='depth',

                 help='create a shallow clone with given depth; see git clone')

# Tool    # 增加Manifest options这一项的帮助信息

group = init_optparse.add_option_group('repo Version options')

group.add_option('--repo-url',

                 dest='repo_url',

                 help='repo repository location', metavar='URL')

group.add_option('--repo-branch',

                 dest='repo_branch',

                 help='repo branch or revision', metavar='REVISION')

group.add_option('--no-repo-verify',

                 dest='no_repo_verify', action='store_true',

                 help='do not verify repo source code')

class CloneFailure(Exception): #定义类 CloneFailure

  """Indicate the remote clone of repo itself failed. # 类文档

  """

def _Init(args): #类方法

  """Installs repo by cloning it over the network. #方法文档

  """

  opt, args = init_optparse.parse_args(args) #如果参数中没有manifest_url，打印usage，退出

  if args or not opt.manifest_url:

    init_optparse.print_usage()

    sys.exit(1)

  url = opt.repo_url #如果没有配置--repo-url的REPO URL，就用默认变量REPO_URL的值 REPO_URL='ssh://username@61.143.53.198/git_repo/repo.git'

  if not url:

    url = REPO_URL

    extra_args.append('--repo-url=%s' % url)

  branch = opt.repo_branch #如果没有配置repo branch分支，就用默认变量REPO_REV的值 REPO_REV="master"

  if not branch:

    branch = REPO_REV

    extra_args.append('--repo-branch=%s' % branch)

  if branch.startswith('refs/heads/'): #对分支名进行check，如果带有refs/heads/这种前缀，就去掉比如说如果branch=refs/heads/master ，就把branch=master

    branch = branch[len('refs/heads/'):]

  if branch.startswith('refs/'):

    print >>sys.stderr, "fatal: invalid branch name '%s'" % branch

    raise CloneFailure()

  if not os.path.isdir(repodir): #repodir=".repo" #如果不存在.repo这个目录，就尝试创建这个.repo这个目录

    try:

      os.mkdir(repodir)

    except OSError, e:

      print >>sys.stderr, \

            'fatal: cannot make %s directory: %s' % (

            repodir, e.strerror)

      # Don't faise CloneFailure; that would delete the

      # name. Instead exit immediately.

      #

      sys.exit(1)

  _CheckGitVersion() #检测GIT的版本

  try:

    if _NeedSetupGnuPG():

      can_verify = _SetupGnuPG(opt.quiet)

    else:

      can_verify = True

    dst = os.path.abspath(os.path.join(repodir, S_repo))

    _Clone(url, dst, opt.quiet)

    if can_verify and not opt.no_repo_verify:

      rev = _Verify(dst, branch, opt.quiet)

    else:

      rev = 'refs/remotes/origin/%s^0' % branch

   # _Checkout(dst, branch, rev, opt.quiet)

  except CloneFailure:

    if opt.quiet:

      print >>sys.stderr, \

        'fatal: repo init failed; run without --quiet to see why'

    raise

def _CheckGitVersion():  #执行命令 git --version 取出得到的值，跟MIN_GIT_VERSION的值进行比较，这个变量的值是（1,5,4）也就是1.5.4，如果低于这个版本，将无法使用repo下载源码

  cmd = [GIT, '--version'] # 在《Ubuntu12.04 搭建GIT环境 下载Softwinner A10源代码》一文中，提到过，如果git版本过低的解决办法

  proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)

  ver_str = proc.stdout.read().strip()

  proc.stdout.close()

  proc.wait()

  if not ver_str.startswith('git version '):

    print >>sys.stderr, 'error: "%s" unsupported' % ver_str

    raise CloneFailure()

  ver_str = ver_str[len('git version '):].strip()

  ver_act = tuple(map(lambda x: int(x), ver_str.split('.')[0:3]))

  if ver_act < MIN_GIT_VERSION:

    need = '.'.join(map(lambda x: str(x), MIN_GIT_VERSION))

    print >>sys.stderr, 'fatal: git %s or later required' % need

    raise CloneFailure()

def _NeedSetupGnuPG():  #如果不存在目录home_dot_repo 也就是/home/user/.repoconfig这个目录的话，返回true，表示需要创建

  if not os.path.isdir(home_dot_repo):

    return True

  kv = os.path.join(home_dot_repo, 'keyring-version') #如果存在/home/user/.repoconfig这个目录，查找下一级的keyring-version

  if not os.path.exists(kv):

    return True

  kv = open(kv).read() #打开/home/user/.repoconfig/keyring-version这个文件不成功，任然返回true

  if not kv:

    return True

  kv = tuple(map(lambda x: int(x), kv.split('.')))#解析出的版本过低 小于KEYRING_VERSION （1 , 0）

  if kv < KEYRING_VERSION:

    return True

  return False # 这些验证都通过才返回false

def _SetupGnuPG(quiet): # 如果_CheckGitVersion()验证没通过，接着就要_SetupGnuPG创建相应的文件，比如/home/user/.repoconfig/keyring-version，结合_CheckGitVersion()的分析，很容易弄明白

  if not os.path.isdir(home_dot_repo):

    try:

      os.mkdir(home_dot_repo)

    except OSError, e:

      print >>sys.stderr, \

            'fatal: cannot make %s directory: %s' % (

            home_dot_repo, e.strerror)

      sys.exit(1)

  if not os.path.isdir(gpg_dir):

    try:

      os.mkdir(gpg_dir, 0700)

    except OSError, e:

      print >>sys.stderr, \

            'fatal: cannot make %s directory: %s' % (

            gpg_dir, e.strerror)

      sys.exit(1)

  env = os.environ.copy()

  env['GNUPGHOME'] = gpg_dir.encode()

  cmd = ['gpg', '--import']

  try:

    proc = subprocess.Popen(cmd,

                            env = env,

                            stdin = subprocess.PIPE)

  except OSError, e:

    if not quiet:

      print >>sys.stderr, 'warning: gpg (GnuPG) is not available.'

      print >>sys.stderr, 'warning: Installing it is strongly encouraged.'

      print >>sys.stderr

    return False

  proc.stdin.write(MAINTAINER_KEYS)

  proc.stdin.close()

  if proc.wait() != 0:

    print >>sys.stderr, 'fatal: registering repo maintainer keys failed'

    sys.exit(1)

  print

  fd = open(os.path.join(home_dot_repo, 'keyring-version'), 'w')

  fd.write('.'.join(map(lambda x: str(x), KEYRING_VERSION)) + '\n')

  fd.close()

  return True

def _SetConfig(local, name, value): # 执行git config [name value]命令

  """Set a git configuration option to the specified value.

  """

  cmd = [GIT, 'config', name, value] 

  if subprocess.Popen(cmd, cwd = local).wait() != 0:

    raise CloneFailure()

def _InitHttp():

  handlers = []

  mgr = urllib2.HTTPPasswordMgrWithDefaultRealm() #Basic认证

  try:

    import netrc

    n = netrc.netrc()

    for host in n.hosts:

      p = n.hosts[host]

      mgr.add_password(None, 'http://%s/' % host, p[0], p[2])

      mgr.add_password(None, 'https://%s/' % host, p[0], p[2])

  except:

    pass

  handlers.append(urllib2.HTTPBasicAuthHandler(mgr))

  if 'http_proxy' in os.environ:

    url = os.environ['http_proxy']

    handlers.append(urllib2.ProxyHandler({'http': url, 'https': url}))

  if 'REPO_CURL_VERBOSE' in os.environ:

    handlers.append(urllib2.HTTPHandler(debuglevel=1))

    handlers.append(urllib2.HTTPSHandler(debuglevel=1))

  urllib2.install_opener(urllib2.build_opener(*handlers))

def _Fetch(url, local, src, quiet): #此方法相当于在终端执行git fetch命令

  if not quiet:

    print >>sys.stderr, 'Get %s' % url

  cmd = [GIT, 'fetch']

  if quiet:

    cmd.append('--quiet')

    err = subprocess.PIPE

  else:

    err = None

  cmd.append(src)

  cmd.append('+refs/heads/*:refs/remotes/origin/*')

  cmd.append('refs/tags/*:refs/tags/*')

  proc = subprocess.Popen(cmd, cwd = local, stderr = err)

  if err:

    proc.stderr.read()

    proc.stderr.close()

  if proc.wait() != 0:

    raise CloneFailure()

def _DownloadBundle(url, local, quiet):

  if not url.endswith('/'): #给url最后添加/clone.bundle

    url += '/'

  url += 'clone.bundle'

  proc = subprocess.Popen(

    [GIT, 'config', '--get-regexp', 'url.*.insteadof'],

    cwd = local,

    stdout = subprocess.PIPE)

  for line in proc.stdout:

    m = re.compile(r'^url\.(.*)\.insteadof (.*)$').match(line)

    if m:

      new_url = m.group(1)

      old_url = m.group(2)

      if url.startswith(old_url):

        url = new_url + url[len(old_url):]

        break

  proc.stdout.close()

  proc.wait()

  if not url.startswith('http:') and not url.startswith('https:'): #检查url是以http或https开头的

    return False

  dest = open(os.path.join(local, '.git', 'clone.bundle'), 'w+b') #打开目标clone.bundle

  try:

    try:

      r = urllib2.urlopen(url) # 开始进行HTTP协议的通信

    except urllib2.HTTPError, e:

      if e.code == 404:

        return False

      print >>sys.stderr, 'fatal: Cannot get %s' % url

      print >>sys.stderr, 'fatal: HTTP error %s' % e.code

      raise CloneFailure()

    except urllib2.URLError, e:

      print >>sys.stderr, 'fatal: Cannot get %s' % url

      print >>sys.stderr, 'fatal: error %s' % e.reason

      raise CloneFailure()

    try:

      if not quiet:

        print >>sys.stderr, 'Get %s' % url

      while True:

        buf = r.read(8192)

        if buf == '':

          return True

        dest.write(buf) # 把下载的文件写到local指定的路径

    finally:

      r.close()

  finally:

    dest.close()

def _ImportBundle(local): #导入已经下载好的bundle

  path = os.path.join(local, '.git', 'clone.bundle')

  try:

    _Fetch(local, local, path, True)

  finally:

    os.remove(path)

def _Clone(url, local, quiet): # 根据url的地址，逐个进行git clone的操作，把代码从仓库中clone下来

  """Clones a git repository to a new subdirectory of repodir

  """

  loc=local.replace('.repo/repo','.repo')

  try:

    os.mkdir(loc)

  except OSError, e:

    print >>sys.stderr, 'creat :%s' % loc

          

    #raise CloneFailure()

  print >>sys.stderr, "git clone repo from % s" % REPO_URL 

  cmd = [GIT, 'clone', REPO_URL]

  try:

    proc = subprocess.Popen(cmd, cwd = loc)

  except OSError, e:

    print >>sys.stderr

    print >>sys.stderr, "fatal: '%s' is not available" % GIT

    print >>sys.stderr, 'fatal: %s' % e

    print >>sys.stderr

    print >>sys.stderr, 'Please make sure %s is installed'\

                        ' and in your path.' % GIT

    raise CloneFailure()

  if proc.wait() != 0:

    print >>sys.stderr, 'fatal: could not create %s' % local

    raise CloneFailure()

  _InitHttp()

  _SetConfig(local, 'remote.origin.url', url)

  _SetConfig(local, 'remote.origin.fetch',

                    '+refs/heads/*:refs/remotes/origin/*')

  if _DownloadBundle(url, local, quiet):

    _ImportBundle(local)

  else:

    _Fetch(url, local, 'origin', quiet)

def _Verify(cwd, branch, quiet): # 确认当前分支branch的tag

  """Verify the branch has been signed by a tag.

  """

  cmd = [GIT, 'describe', 'origin/%s' % branch]

  proc = subprocess.Popen(cmd,

                          stdout=subprocess.PIPE,

                          stderr=subprocess.PIPE,

                          cwd = cwd)

  cur = proc.stdout.read().strip()

  proc.stdout.close()

  proc.stderr.read()

  proc.stderr.close()

  if proc.wait() != 0 or not cur:

    print >>sys.stderr

    print >>sys.stderr,\

      "fatal: branch '%s' has not been signed" \

      % branch

    raise CloneFailure()

  m = re.compile(r'^(.*)-[0-9]{1,}-g[0-9a-f]{1,}$').match(cur) #正则表达式解析 ^ 开始符 (.*)表示任意个数的字符 [0-9]{1,} [0,9]表示是数字 {1,}表示个数至少是1个，也可能是成千上万 [0-9a-f]{1,} 表示是个数大于1的十六进制字符的字符串 $表示结束符

  if m:

    cur = m.group(1)

    if not quiet:

      print >>sys.stderr

      print >>sys.stderr, \

        "info: Ignoring branch '%s'; using tagged release '%s'" \

        % (branch, cur)

      print >>sys.stderr

  env = os.environ.copy() #获取环境变量

  env['GNUPGHOME'] = gpg_dir.encode()

  cmd = [GIT, 'tag', '-v', cur] # 执行git tag -v   验证gpg签名的tag

  proc = subprocess.Popen(cmd,

                          stdout = subprocess.PIPE,

                          stderr = subprocess.PIPE,

                          cwd = cwd,

                          env = env)

  out = proc.stdout.read()

  proc.stdout.close()

  err = proc.stderr.read()

  proc.stderr.close()

  if proc.wait() != 0:

    print >>sys.stderr

    print >>sys.stderr, out

    print >>sys.stderr, err

    print >>sys.stderr

    raise CloneFailure()

  return '%s^0' % cur

def _Checkout(cwd, branch, rev, quiet): # 相当于执行git checkout

  """Checkout an upstream branch into the repository and track it.

  """

  cmd = [GIT, 'update-ref', 'refs/heads/default', rev]

  if subprocess.Popen(cmd, cwd = cwd).wait() != 0:

    raise CloneFailure()

  _SetConfig(cwd, 'branch.default.remote', 'origin')

  _SetConfig(cwd, 'branch.default.merge', 'refs/heads/%s' % branch)

  cmd = [GIT, 'symbolic-ref', 'HEAD', 'refs/heads/default']

  if subprocess.Popen(cmd, cwd = cwd).wait() != 0:

    raise CloneFailure()

  cmd = [GIT, 'read-tree', '--reset', '-u']

  if not quiet:

    cmd.append('-v')

  cmd.append('HEAD')

  if subprocess.Popen(cmd, cwd = cwd).wait() != 0:

    raise CloneFailure()

def _FindRepo():

  """Look for a repo installation, starting at the current directory.

  """

  dir = os.getcwd() #获取当前目录

  repo = None

  olddir = None # 在当前目录循环查找main.py

  while dir != '/' \

    and dir != olddir \

    and not repo:

    repo = os.path.join(dir, repodir, REPO_MAIN) #/home/user/.repo/repo/main.py主入口

    if not os.path.isfile(repo):

      repo = None

      olddir = dir

      dir = os.path.dirname(dir)

  return (repo, os.path.join(dir, repodir))

class _Options: #Options 类

  help = False

def _ParseArguments(args): # 解析参数

  cmd = None

  opt = _Options()

  arg = []

  for i in xrange(0, len(args)):

    a = args[i]

    if a == '-h' or a == '--help':

      opt.help = True

    elif not a.startswith('-'):

      cmd = a

      arg = args[i + 1:]

      break

  return cmd, opt, arg

def _Usage():

  print >>sys.stderr,\

"""usage: repo COMMAND [ARGS]

repo is not yet installed. Use "repo init" to install it here.

The most commonly used repo commands are:

  init Install repo in the current working directory

  help Display detailed help on a command

For access to the full online help, install repo ("repo init").

"""

  sys.exit(1)

def _Help(args):

  if args:

    if args[0] == 'init':

      init_optparse.print_help()

      sys.exit(0)

    else:

      print >>sys.stderr,\

      "error: '%s' is not a bootstrap command.\n"\

      ' For access to online help, install repo ("repo init").'\

      % args[0]

  else:

    _Usage()

  sys.exit(1)

def _NotInstalled():

  print >>sys.stderr,\

'error: repo is not installed. Use "repo init" to install it here.'

  sys.exit(1)

def _NoCommands(cmd):

  print >>sys.stderr,\

"""error: command '%s' requires repo to be installed first.

       Use "repo init" to install it here.""" % cmd

  sys.exit(1)

def _RunSelf(wrapper_path):

  my_dir = os.path.dirname(wrapper_path)

  my_main = os.path.join(my_dir, 'main.py')

  my_git = os.path.join(my_dir, '.git')

  if os.path.isfile(my_main) and os.path.isdir(my_git):

    for name in ['git_config.py',

                 'project.py',

                 'subcmds']:

      if not os.path.exists(os.path.join(my_dir, name)):

        return None, None

    return my_main, my_git

  return None, None

def _SetDefaultsTo(gitdir):

  global REPO_URL

  global REPO_REV

  REPO_URL = gitdir

  proc = subprocess.Popen([GIT,

                           '--git-dir=%s' % gitdir,

                           'symbolic-ref',

                           'HEAD'],

                          stdout = subprocess.PIPE,

                          stderr = subprocess.PIPE)

  REPO_REV = proc.stdout.read().strip()

  proc.stdout.close()

  proc.stderr.read()

  proc.stderr.close()

  if proc.wait() != 0:

    print >>sys.stderr, 'fatal: %s has no current branch' % gitdir

    sys.exit(1)

def main(orig_args):

  main, dir = _FindRepo()

  cmd, opt, args = _ParseArguments(orig_args)

  wrapper_path = os.path.abspath(__file__)

  my_main, my_git = _RunSelf(wrapper_path)

  if not main:

    if opt.help:

      _Usage()

    if cmd == 'help':

      _Help(args)

    if not cmd:

      _NotInstalled()

    if cmd == 'init':

      if my_git:

        _SetDefaultsTo(my_git)

      try:

        _Init(args)

      except CloneFailure:

        for root, dirs, files in os.walk(repodir, topdown=False):

          for name in files:

            os.remove(os.path.join(root, name))

          for name in dirs:

            os.rmdir(os.path.join(root, name))

        os.rmdir(repodir)

        sys.exit(1)

      main, dir = _FindRepo()

    else:

      _NoCommands(cmd)

  if my_main:

    main = my_main

  ver_str = '.'.join(map(lambda x: str(x), VERSION))

  me = [main,

        '--repo-dir=%s' % dir,

        '--wrapper-version=%s' % ver_str,

        '--wrapper-path=%s' % wrapper_path,

        '--']

  me.extend(orig_args)

  me.extend(extra_args)

  try:

    os.execv(main, me)

  except OSError, e:

    print >>sys.stderr, "fatal: unable to start %s" % main

    print >>sys.stderr, "fatal: %s" % e

    sys.exit(148)

if __name__ == '__main__':

  main(sys.argv[1:])