webrtc代码管理工具gclient入门

google的chromium项目是用gclient来管理源码的checkout, update等。 gclient是google专门为这种多源项目编写的脚本，它可以将多个源码管理系统中的代码放在一起管理。甚至包括将Git和svn代码放在一起。

webrtc也是使用gclient管理代码.

gclient的sync，update等命令密切相关的两类文件.gclient和DEPS。

.gclient文件是gclient的控制文件，该文件放在工作目录的最上层(webrtc环境下与src统计目录)。".gclient"文件是一个Python的脚本，定义了一组"solutions"，格式类似如下

solutions = [  
  { "name"        : "src",  
    "url"         : "svn://svnserver/component/trunk/src",  
    "custom_deps" : {  
      # To use the trunk of a component instead of what's in DEPS:  
      #"component": "https://svnserver/component/trunk/",  
      # To exclude a component from your working copy:  
      #"data/really_large_component": None,  
    }  
  },  
]  

• name:checkout出源码的名字
• url:源码所在的目录,gclient希望checkout出的源码中包括一个DEPS的文件,这个文件包含了必须checkout到工作目录的源码信息;
• deps_file:这是一个文件名(不包括路径),指在工程目录中包含依赖列表的文件,该项可选,默认值为"DEPS"

• custom_deps:这是一个可选的字典对象,会覆盖工程的"DEPS"文件定义的条目.一般它用作本地目录中,那些不用checkout的代码,或者让本地目录从不同位置checkout一个新的代码出来,或者checkout不同的分支,版本等.也可以用于增加在DEPS中不存在的新的项目.如:

  "custom_deps": {  
  "src/content/test/data/layout_tests/LayoutTests": None,  
  "src/chrome/tools/test/reference_build/chrome_win": None,  
  "src/chrome_frame/tools/test/reference_build/chrome_win": None,  
  "src/chrome/tools/test/reference_build/chrome_linux": None,  
  "src/chrome/tools/test/reference_build/chrome_mac": None,  
  "src/third_party/hunspell_dictionaries": None,  
  },  

• target_os:这个可选的条目可以指出特殊的平台,根据平台类checkout出不同代码,如:

  target_os = ['android']  

  如果target_os_only值为True的话,那么,仅仅checkout出对应的代码,如:

  target_os = [ "ios" ]  
  target_os_only = True

在每个checkout出的工程中，gclient期望发现一个DEPS文件（由deps_file来给定），它定义了工程不同部分都是如何checkout出来。
“DEPS”也是一个python脚本，最简单的，如下：

deps = {  
  "src/outside" : "http://outside-server/trunk@1234",  
  "src/component" : "svn://svnserver/component/trunk/src@77829",  
  "src/relative" : "/trunk/src@77829",  
}  

deps的每个条目都包含一个key-value对，key是被checkout的本地目录，而value就是对应的远程URL。如果路径是以'/'开头的，那么它是一个相对URL，相对与.gclient中URL地址。

URL通常包含一个版本号，以便锁定源码在特定版本上。当然，这是可选的。如果没有，那么它将获取指定分支上最新的版本。

DEPS还可以包含其他类型的数据，如vars,

vars = {
  'pymox':
    'http://pymox.googlecode.com/svn',
  'sfntly':
    'http://sfntly.googlecode.com/svn',
  'eyes-free':
    'http://eyes-free.googlecode.com/svn',
  'rlz':
    'http://rlz.googlecode.com/svn',
  'smhasher':
    'http://smhasher.googlecode.com/svn',
...
}

vars定义了一组变量，在后面，可以通过Var(xxx)来访问。Var(xxx)返回一个字符串，故此，也可以进行操作，如

'src/third_party/cros_dbus_cplusplus/source':
Var("git.chromium.org") + '/chromiumos/third_party/dbus-cplusplus.git@5e8f6d9db5c2abfb91d91f751184f25bb5cd0900',
'src/third_party/WebKit':
Var("webkit_trunk")[:-6] + '/branches/chromium/1548@153044',

第二个自立，Var("webkit_trunk")[:-6]是一个python表达式，表示取得"webkit_trunk"表示的字符串的最后6个
Hooks：DEPS包含可选的内容 hooks，也有重要的作用，它表示在sync, update或者recert后，执行一个hook操作。
如果使用 --nohooks选项（hook默认执行），那么在gclient sync或者其他操作后，不会执行hook。你可以通过gclient runhooks来单独执行； 如果有 gclient sync --force，那么，无论sync是否成功，都会执行hook。
hook在DEPS中的写法，一般是：

hooks = [
  { "pattern": "\\.(gif|jpe?g|pr0n|png)$",
    "action":  ["python", "image_indexer.py", "--all"]},
  { "pattern": ".",
    "name": "gyp",
    "action":  ["python", "src/build/gyp_chromium"]},
]

hooks包含一组hook，每个hook有几个重要项:

• pattern 是一个正则表达式，用来匹配工程目录下的文件，一旦匹配成功，action项就会执行
• action 描述一个根据特定参数运行的命令行。这个命令在每次gclient时，无论多少文件匹配，至多运行一次。这个命令和.gclient在同一目录下运行。如果第一个参数是"python"，那么，当前的python解释器将被使用。如果包含字符串 "$matching_files"，它将该字符串扩展为匹配出的文件列表。
• name 可选，标记出hook所属的组，可以被用来覆盖和重新组织。

deps_os： DEPS中定义不同平台依赖关系的项目，如

deps_os = {
  "win": {
    "src/chrome/tools/test/reference_build/chrome_win":
      "/trunk/deps/reference_builds/chrome_win@197743",

    "src/third_party/cygwin":
      "/trunk/deps/third_party/cygwin@133786",

.....
  },

  "ios": {
    "src/third_party/GTM":
      (Var("googlecode_url") % "google-toolbox-for-mac") + "/trunk@" +
      Var("gtm_revision"),

    "src/third_party/nss":
      "/trunk/deps/third_party/nss@" + Var("nss_revision"),
....
   },
...
}

deps_os指定不同平台的依赖，它可以包含多种平台，和.gclient中的target_os对应。这种对应关系如下：

  DEPS_OS_CHOICES = {
    "win32": "win",
    "win": "win",
    "cygwin": "win",
    "darwin": "mac",
    "mac": "mac",
    "unix": "unix",
    "linux": "unix",
    "linux2": "unix",
    "linux3": "unix",
    "android": "android",
  }

下载webrtc android代码的.gclient文件(与src同级目录):

solutions = [
  {
    "url": "https://chromium.googlesource.com/external/webrtc.git",
    "managed": False,
    "name": "src",
    "deps_file": "DEPS",
    "custom_deps": {},
  },
]
target_os = ["android", "unix"]

src同级目录下.gclient_entries定义了各模块及对应地址

entries = {
  'src': 'https://chromium.googlesource.com/external/webrtc.git',
  'src/base': 'https://chromium.googlesource.com/chromium/src/base@413df39df4640665d7ee1e8c198be1e91cedb4d9',
  'src/build': 'https://chromium.googlesource.com/chromium/src/build@98f2769027214c848094d0d58156474eada3bc1b',
  'src/buildtools': 'https://chromium.googlesource.com/chromium/buildtools.git@98f00fa10dbad2cdbb2e297a66c3d6d5bc3994f3',
  'src/testing': 'https://chromium.googlesource.com/chromium/src/testing@3eab1a4b0951ac1fcb2be8bf9cb24143b509ea52',
  'src/testing/gmock': 'https://chromium.googlesource.com/external/googlemock.git@0421b6f358139f02e102c9c332ce19a33faf75be',
  'src/testing/gtest': 'https://chromium.googlesource.com/external/github.com/google/googletest.git@6f8a66431cb592dad629028a50b3dd418a408c87',
  'src/third_party': 'https://chromium.googlesource.com/chromium/src/third_party@939f3a2eae486dd7cf3b31eae38642d2bc243737',
  'src/third_party/android_tools': 'https://chromium.googlesource.com/android_tools.git@b65c4776dac2cf1b80e969b3b2d4e081b9c84f29',
  'src/third_party/boringssl/src': 'https://boringssl.googlesource.com/boringssl.git@777fdd6443d5f01420b67137118febdf56a1c8e4',
  'src/third_party/catapult': 'https://chromium.googlesource.com/external/github.com/catapult-project/catapult.git@6939b1db033bf35f4adf1ee55824b6edb3e324d6',
  'src/third_party/ced/src': 'https://chromium.googlesource.com/external/github.com/google/compact_enc_det.git@e21eb6aed10b9f6e2727f136c52420033214d458',
  'src/third_party/colorama/src': 'https://chromium.googlesource.com/external/colorama.git@799604a1041e9b3bc5d2789ecbd7e8db2e18e6b8',
  'src/third_party/ffmpeg': 'https://chromium.googlesource.com/chromium/third_party/ffmpeg.git@28a5cdde5c32bcf66715343c10f74e85713f7aaf',
  'src/third_party/gflags': 'https://chromium.googlesource.com/external/webrtc/deps/third_party/gflags@892576179b45861b53e04a112996a738309cf364',
  'src/third_party/gflags/src': 'https://chromium.googlesource.com/external/github.com/gflags/gflags@03bebcb065c83beff83d50ae025a55a4bf94dfca',
  'src/third_party/gtest-parallel': 'https://chromium.googlesource.com/external/github.com/google/gtest-parallel@7eb02a6415979ea59e765c34fe9da6c792f53e26',
  'src/third_party/icu': 'https://chromium.googlesource.com/chromium/deps/icu.git@b34251f8b762f8e2112a89c587855ca4297fed96',
  'src/third_party/jsoncpp/source': 'https://chromium.googlesource.com/external/github.com/open-source-parsers/jsoncpp.git@f572e8e42e22cfcf5ab0aea26574f408943edfa4',
  'src/third_party/jsr-305/src': 'https://chromium.googlesource.com/external/jsr-305.git@642c508235471f7220af6d5df2d3210e3bfc0919',
  'src/third_party/junit/src': 'https://chromium.googlesource.com/external/junit.git@64155f8a9babcfcf4263cf4d08253a1556e75481',
  'src/third_party/libFuzzer/src': 'https://chromium.googlesource.com/chromium/llvm-project/llvm/lib/Fuzzer.git@16f5f743c188c836d32cdaf349d5d3effb8a3518',
  'src/third_party/libjpeg_turbo': 'https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@7260e4d8b8e1e40b17f03fafdf1cd83296900f76',
  'src/third_party/libsrtp': 'https://chromium.googlesource.com/chromium/deps/libsrtp.git@ccf84786f8ef803cb9c75e919e5a3976b9f5a672',
  'src/third_party/libvpx/source/libvpx': 'https://chromium.googlesource.com/webm/libvpx.git@f22b828d685adee4c7a561990302e2d21b5e0047',
  'src/third_party/libyuv': 'https://chromium.googlesource.com/libyuv/libyuv.git@fc02cc3806a394a6b887979ba74aa49955f3199b',
  'src/third_party/lss': 'https://chromium.googlesource.com/linux-syscall-support.git@63f24c8221a229f677d26ebe8f3d1528a9d787ac',
  'src/third_party/mockito/src': 'https://chromium.googlesource.com/external/mockito/mockito.git@de83ad4598ad4cf5ea53c69a8a8053780b04b850',
  'src/third_party/openh264/src': 'https://chromium.googlesource.com/external/github.com/cisco/openh264@0fd88df93c5dcaf858c57eb7892bd27763f0f0ac',
  'src/third_party/openmax_dl': 'https://chromium.googlesource.com/external/webrtc/deps/third_party/openmax.git@7acede9c039ea5d14cf326f44aad1245b9e674a7',
  'src/third_party/requests/src': 'https://chromium.googlesource.com/external/github.com/kennethreitz/requests.git@f172b30356d821d180fa4ecfa3e71c7274a32de4',
  'src/third_party/robolectric/robolectric': 'https://chromium.googlesource.com/external/robolectric.git@2a0b6ba221c14f3371813a676ce06143353e448d',
  'src/third_party/ub-uiautomator/lib': 'https://chromium.googlesource.com/chromium/third_party/ub-uiautomator.git@00270549ce3161ae72ceb24712618ea28b4f9434',
  'src/third_party/usrsctp/usrsctplib': 'https://chromium.googlesource.com/external/github.com/sctplab/usrsctp@8679f2b0bf063ac894dc473debefd61dbbebf622',
  'src/third_party/yasm/source/patched-yasm': 'https://chromium.googlesource.com/chromium/deps/yasm/patched-yasm.git@7da28c6c7c6a1387217352ce02b31754deb54d2a',
  'src/tools': 'https://chromium.googlesource.com/chromium/src/tools@4718dd2b6d53fb68819b3fd23676b40935f4f31e',
  'src/tools/gyp': 'https://chromium.googlesource.com/external/gyp.git@eb296f67da078ec01f5e3a9ea9cdc6d26d680161',
  'src/tools/swarming_client': 'https://chromium.googlesource.com/external/swarming.client.git@11e31afa5d330756ff87aa12064bb5d032896cb5',
  'src/buildtools/clang_format/script': 'https://chromium.googlesource.com/chromium/llvm-project/cfe/tools/clang-format.git@c09c8deeac31f05bd801995c475e7c8070f9ecda',
  'src/buildtools/third_party/libc++/trunk': 'https://chromium.googlesource.com/chromium/llvm-project/libcxx.git@b1ece9c037d879843b0b0f5a2802e1e9d443b75a',
  'src/buildtools/third_party/libc++abi/trunk': 'https://chromium.googlesource.com/chromium/llvm-project/libcxxabi.git@0edb61e2e581758fc4cd4cd09fc588b3fc91a653',
  'src/third_party/android_tools/ndk': 'https://chromium.googlesource.com/android_ndk.git@26d93ec07f3ce2ec2cdfeae1b21ee6f12ff868d8',
}