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首先说一下为什么会想分享这篇博客。出发点很简单，只是想学习一下Python在AOSP中的应用。repo应用就是一个研究的切入点。其次Python在深度学习、大数据都有一定的支持，后续会研究一下这方面的技术。最后就是个人喜好，无他。
repo就是通过Python封装git命令的应用。什么是repo？简单来说就是对AOSP含有git仓库的各个项目的批处理。repo应用包括repo仓库（仓库也可以叫做项目）、manifest仓库、projectsc仓库集这三个核心。repo仓库都是一些Python文件，manifest仓库只有一个存放AOSP各个子项目元数据的xml文件。projects仓库集是AOSP各个子项目对应的git仓库。
下面用一张图片表示一下。
补充一点，git是允许repository和working directory分布在不同的目录下的。所以就会看到AOSP的working directory在项目根目录而.git目录在.repo/projects目录
先来草率的分析一下,拉取一套AOSP代码应该按照如下流程：
mkdir testsource #创建AOSP目录。用于存放.repo应用和源码
cd testsource
repo init -u https://android.googlesource.com/platform/manifest -b android-4.0.1_r1
cmd #初始化repo仓库和manifest仓库
repo sync -j 8
cmd #同步projects仓库集
repo start master --all
cmd #创建并且切换到新分支上
repo仓库初始化--->manifest仓库初始化--->project仓库集初始化--->创建并切换到新分支上
从数据流自上而下看：
repo command line --->optparse--->git command line
在Python中使用的是optparse模块（后续将被argparse模块取代）解析命令行，所以optparse模块相当于数据转换中心将repo命名行转成git命令行
Repo仓库
接下来就看看具体的细节处理，从repo模块的入口函数main开始，执行的命令行如下：
repo init -u https://android.googlesource.com/platform/manifest -b android-4.0.1_r1
def main(orig_args):
cmd, opt, args = _ParseArguments(orig_args)
repo_main, rel_repo_dir = None, None
# Don't use the local repo copy, make sure to switch to the gitc client first.
if cmd != 'gitc-init':
repo_main, rel_repo_dir = _FindRepo()
wrapper_path = os.path.abspath(__file__)
my_main, my_git = _RunSelf(wrapper_path)
cwd = os.getcwd()
...
if not repo_main:
if opt.help:
_Usage()
if cmd == 'help':
_Help(args)
if not cmd:
_NotInstalled()
if cmd == 'init' or cmd == 'gitc-init':
if my_git:
_SetDefaultsTo(my_git)
try:
_Init(args, gitc_init=(cmd == 'gitc-init'))
except CloneFailure:
...
sys.exit(1)
repo_main, rel_repo_dir = _FindRepo()
else:
_NoCommands(cmd)
if my_main:
repo_main = my_main
ver_str = '.'.join(map(str, VERSION))
me = [sys.executable, repo_main,
'--repo-dir=%s' % rel_repo_dir,
'--wrapper-version=%s' % ver_str,
'--wrapper-path=%s' % wrapper_path,
'--']
me.extend(orig_args)
me.extend(extra_args)
try:
os.execv(sys.executable, me)
except OSError as e:
...
sys.exit(148)
repo模块函数main(sys.argv[1:]) 参数sys.argv[1:]就是由command、options组成，然后由_ParseArguments函数解析。由于main函数流程复杂，我们考虑的是初次初始化。main函数在调用_Init函数之前对环境进行了检查：repo模块的版本号和路径、.repo/repo/路径下的main模块和git仓库。在_Init函数之后就是执行main模块中的入口函数_Main
_ParseArguments函数的代码如下：
def _ParseArguments(args):
cmd = None
opt = _Options()
arg = []
for i in range(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
_ParseArguments函数解析出cmd、opt、args，其中,cmd是init，args是command（init）后面的参数（-u https://android.googlesource.com/platform/manifest -b android-4.0.1_r1），而opt特指-h（–help）这样的用意在于当你输入repo -h,–help时就可以弹出一些帮助文档。
_FindRepo函数的代码如下：
def _FindRepo():
"""Look for a repo installation, starting at the current directory.
"""
curdir = os.getcwd()
repo = None
olddir = None
while curdir != '/' \
and curdir != olddir \
and not repo:
repo = os.path.join(curdir, repodir, REPO_MAIN)
if not os.path.isfile(repo):
repo = None
olddir = curdir
curdir = os.path.dirname(curdir)
return (repo, os.path.join(curdir, repodir))
_FindRepo函数查找当前执行repo命令的目录下.repo/repo/main.py和.repo目录两者是否都存在。
_RunSelf函数的代码如下：
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
_RunSelf函数检查repo模块的同级目录里是否有三个文件main.py 、git_config.py、project.py 和两个目录subcmds、.git。这次是查找运行中模块repo的同级目录，是否具备三个文件两个目录，如有具备这些，则.repo仓库之前就已经被初始化过了。反之，接下去就会初始化仓库。
接下来的各种控制流判断，取其中两个关键函数_SetDefaultsTo和_Init来详细讲解
...
if not repo_main:
...
if cmd == 'init' or cmd == 'gitc-init':
if my_git:
_SetDefaultsTo(my_git)
try:
_Init(args, gitc_init=(cmd == 'gitc-init'))
...
repo_main,cmd,my_git这三个变量我们前面已经说过了它们的由来,其中的my_git如果存在，调用_SetDefaultsTo函数会设置数据源，反之，就是初次初始化，使用默认的数据源（REPO_URL = ‘https://gerrit.googlesource.com/git-repo’ ），那么就会克隆一个.repo/repo/仓库
_SetDefaultsTo函数
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('fatal: %s has no current branch' % gitdir, file=sys.stderr)
sys.exit(1)
--git-dir 指定git仓库的位置,symbolic-ref 指定当前分支为克隆分支这两者的值通过关键词global变成全局变量。
接下来就是核心函数_Init如下：
def _Init(args, gitc_init=False):
"""Installs repo by cloning it over the network.
"""
...
opt, args = init_optparse.parse_args(args)
if args:
init_optparse.print_usage()
sys.exit(1)
url = opt.repo_url
if not url:
url = REPO_URL
extra_args.append('--repo-url=%s' % url)
branch = opt.repo_branch
if not branch:
branch = REPO_REV
extra_args.append('--repo-branch=%s' % branch)
if branch.startswith('refs/heads/'):
branch = branch[len('refs/heads/'):]
...
try:
...
os.mkdir(repodir)
except OSError as e:
if e.errno != errno.EEXIST:
...
sys.exit(1)
_CheckGitVersion()
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, not opt.no_clone_bundle)
if not os.path.isfile('%s/repo' % dst):
_print("warning: '%s' does not look like a git-repo repository, is "
"REPO_URL set correctly?" % url, file=sys.stderr)
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:
...
_Init函数的参数 args=[-u,https://android.googlesource.com/platform/manifest,-b,android-4.0.1_r1] ,使用OptionParse类的成员函数parse_args解析得到opt对象（存储有url地址和分支号）和args列表（其值不为空时，便会停止创建仓库的进程）。既然得到了opt对象,那么接下来就要通过指定url地址和分支号去获取repo仓库、manifest仓库，由于命令行只有manifest仓库的地址，那么是不是就没有办法获取repo仓库了吗？google提供了自家repo仓库的url地址（https://gerrit.googlesource.com/git-repo）供开发者使用，也可以使用–repo-url选项指定自家公司repo仓库的url地址。接下来检查和配置环境
- 1.需要支持1.7.2以上的git版本
- 2.没有配置GnuPG的环境下，自动生成GnuPG文件
当GnuPG的环境配置好了，就会返回一个值can_verify，用于判断克隆完repo仓库后验证最新的tag是否被GunPG签过名，然后将克隆下来的repo仓库使用_Checkout函数切换到这个最新的tag，以便于使用最新的release版本（一般发布一个release版本都会打上一个tag），这就是这个tag的用意。
接下来我们就来看看函数_Init调用的两个核心函数_Clone和_Checkout
在这之前我们来看看git对远程仓库的操作图
_Clone函数的代码如下：
def _Clone(url, local, quiet, clone_bundle):
"""Clones a git repository to a new subdirectory of repodir
"""
try:
os.mkdir(local)
except OSError as e:
...
raise CloneFailure()
cmd = [GIT, 'init', '--quiet']
try:
proc = subprocess.Popen(cmd, cwd=local)
except OSError as e:
...
raise CloneFailure()
if proc.wait() != 0:
...
raise CloneFailure()
_InitHttp()
_SetConfig(local, 'remote.origin.url', url)
_SetConfig(local,
'remote.origin.fetch',
'+refs/heads/*:refs/remotes/origin/*')
if clone_bundle and _DownloadBundle(url, local, quiet):
_ImportBundle(local)
_Fetch(url, local, 'origin', quiet)
这里简单说一下_Clone函数的流程图。
创建git仓库(git init)---> 初始化http网络 ----> 配置远程仓库url地址、分支名(git config) ---> fetch记录从remote repository到local repository（git fetch）
在有网络的条件下可以从远程仓库克隆代码，但是如果离线了怎么办？git给我们提供了一种bundle机制。
_DownloadBundle函数的代码如下:
def _DownloadBundle(url, local, quiet):
if not url.endswith('/'):
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:'):
return False
dest = open(os.path.join(local, '.git', 'clone.bundle'), 'w+b')
try:
try:
r = urllib.request.urlopen(url)
except urllib.error.HTTPError as e:
if e.code in [401, 403, 404, 501]:
return False
...
raise CloneFailure()
except urllib.error.URLError as e:
...
raise CloneFailure()
try:
if not quiet:
_print('Get %s' % url, file=sys.stderr)
while True:
buf = r.read(8192)
if buf == '':
return True
dest.write(buf)
finally:
r.close()
finally:
dest.close()
在使用git fetch获取remote repository记录到local repository之前，其实代码的来源还可以从bundle获取。生成bundle之前需要在有网络的条件下，将远程仓库的记录存储在bundle中。
最后会调用_ImportBundle函数导入数据。这种导入方式的应用场景在于环境处于脱机状态，便可以从其他的机器拷贝一份bundle导入到自己的仓库中。_ImportBundle函数是对_Fetch函数进行包装,其中最为重要的就是第三个参数，指定了要导入到local repository的数据来源路径，可以是网络的 url 的仓库名，也可以是本地的bundle路径
_Checkout函数
def _Checkout(cwd, branch, rev, quiet):
"""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()
该函数对git chechout的底层函数进行封装，功能和git checkout切分支是一样的，至此我们的_Init函数就执行完了，并且得到了repo仓库了那么接下来就是要得到manifest仓库了
...
ver_str = '.'.join(map(str, VERSION))
me = [sys.executable, repo_main,
'--repo-dir=%s' % rel_repo_dir,
'--wrapper-version=%s' % ver_str,
'--wrapper-path=%s' % wrapper_path,
'--']
me.extend(orig_args)
me.extend(extra_args)
try:
os.execv(sys.executable, me)
...
Manifest仓库
接下来就是执行main模块函数_Main，执行时命令行如下：
/home/.../.repo/repo/main.py --repo-dir=/home/.../.repo --wrapper-version=1.0 --wrapper-path=/usr/bin/repo -- init -u xxxx -b xxx
其参数argv经过repo模块的扩展，添加了三个信息
- .repo目录的绝对路径
- repo模块内部定义的版本号
- repo模块的绝对路径
经过repo模块添加的信息用来检查是否有可用的repo和执行main模块，这是命令行的前部分，而后半部分（init -u xxxx -b xxx）供直接或间接以Command为基类的衍生类的成员函数Execute调用放置在.repo/repo/subcmds/目录下的*.py模块。repo脚本能执行的命令都是放在该目录下的，一个Python文件对应一个repo命令。比如："repo init"表示要执行的模块在.repo/repo/subcmds/init.py。
_Main函数的代码如下：
def _Main(argv):
result = 0
opt = optparse.OptionParser(usage="repo wrapperinfo -- ...")
opt.add_option("--repo-dir", dest="repodir",
help="path to .repo/")
opt.add_option("--wrapper-version", dest="wrapper_version",
help="version of the wrapper script")
opt.add_option("--wrapper-path", dest="wrapper_path",
help="location of the wrapper script")
_PruneOptions(argv, opt)
opt, argv = opt.parse_args(argv)
_CheckWrapperVersion(opt.wrapper_version, opt.wrapper_path)
_CheckRepoDir(opt.repodir)
Version.wrapper_version = opt.wrapper_version
Version.wrapper_path = opt.wrapper_path
repo = _Repo(opt.repodir)
try:
try:
init_ssh()
init_http()
result = repo._Run(argv) or 0
finally:
close_ssh()
except KeyboardInterrupt:
...
result = 1
except ManifestParseError as mpe:
...
result = 1
except RepoChangedException as rce:
# If repo changed, re-exec ourselves.
#
argv = list(sys.argv)
argv.extend(rce.extra_args)
try:
os.execv(__file__, argv)
except OSError as e:
...
result = 128
sys.exit(result)
if __name__ == '__main__':
_Main(sys.argv[1:])
_Main函数的重点部分在于repo调用_Repo类中的成员函数_Run，而前期也如repo和main两个模块一样做一些必要的检查。修剪命令行的_PruneOptions函数、解析命令的parse_args函数(opt为"–"之前的内容，argv"为–"之后的内容)、检查repo模块版本的_CheckWrapperVersion函数、检查 .repo目录是否存在的_CheckRepoDir函数。
_Repo类的代码如下：
from subcmds import all_commands
class _Repo(object):
def __init__(self, repodir):
self.repodir = repodir
self.commands = all_commands
# add 'branch' as an alias for 'branches'
all_commands['branch'] = all_commands['branches']
def _Run(self, argv):
result = 0
name = None
glob = []
for i in range(len(argv)):
if not argv[i].startswith('-'):
name = argv[i]
if i > 0:
glob = argv[:i]
argv = argv[i + 1:]
break
if not name:
glob = argv
name = 'help'
argv = []
gopts, _gargs = global_options.parse_args(glob)
...
try:
cmd = self.commands[name]
except KeyError:
...
return 1
cmd.repodir = self.repodir
cmd.manifest = XmlManifest(cmd.repodir)
...
Editor.globalConfig = cmd.manifest.globalConfig
...
try:
copts, cargs = cmd.OptionParser.parse_args(argv)
copts = cmd.ReadEnvironmentOptions(copts)
except NoManifestException as e:
...
return 1
...
start = time.time()
try:
result = cmd.Execute(copts, cargs)
except (DownloadError, ManifestInvalidRevisionError,
NoManifestException) as e:
...
result = 1
except NoSuchProjectError as e:
...
result = 1
except InvalidProjectGroupsError as e:
...
result = 1
finally:
elapsed = time.time() - start
hours, remainder = divmod(elapsed, 3600)
minutes, seconds = divmod(remainder, 60)
if gopts.time:
if hours == 0:
print('real\t%dm%.3fs' % (minutes, seconds), file=sys.stderr)
else:
print('real\t%dh%dm%.3fs' % (hours, minutes, seconds),
file=sys.stderr)
return result
_Repo类有两个成员变量repodir、commands和一个类变量all_commands，其中all_commands字典的值是一些repo脚本能够执行命令的类名。那这些值是怎么来的呢 ？ 在 from subcmds import all_commands 时，就会初始化subcmds包，将subcmds目录下所有模块名的首字母转化为大写其余字母不变，就成了命令的类名。再结合成员函数_Run，可以知道，该类的作用在于，将解析后的cmd分发到包subcmds下所对应的模块里面的类（比如：init指令—>subcmds/init.py里面的Init类）。
_Repo类的成员函数_Run主要是初始化XmlManifest，获取某个指令独有OptionParse并解析指令，调用Command类的成员函数Execute。
其中XmlManifest类用于管理 .repo，XmlManifest类的代码如下：
class XmlManifest(object):
"""manages the repo configuration file"""
def __init__(self, repodir):
self.repodir = os.path.abspath(repodir)
self.topdir = os.path.dirname(self.repodir)
self.manifestFile = os.path.join(self.repodir, MANIFEST_FILE_NAME)
self.globalConfig = GitConfig.ForUser()
self.localManifestWarning = False
self.isGitcClient = False
self.repoProject = MetaProject(self, 'repo',
gitdir = os.path.join(repodir, 'repo/.git'),
worktree = os.path.join(repodir, 'repo'))
self.manifestProject = MetaProject(self, 'manifests',
gitdir = os.path.join(repodir, 'manifests.git'),
worktree = os.path.join(repodir, 'manifests'))
XmlManifest类在manifest_xml模块里面，XmlManifest类的主要成员变量有：
- repodir:.repo目录的绝对路径
- topdir：AOSP项目的绝对路径（testsource目录绝对路径）
- manifestFile：.repo目录下的链接文件manifest.xml
- repoProject： .repo目录下的repo仓库
- manifestProject：.repo目录下的manifest仓库
类中还提供了对.repo的属性值和对属性值操作的成员函数，比如加载数据到XmlManifest对象(_Load成员函数)和重置数据(_Unload成员函数)，创建manifest.xml链接文件（Link成员函数），获取projects目录下的仓库对象（GetProjectsWithName，GetProjectPaths成员函数）。所以不难看出该类就是对.repo目录的管理工具。我们在继续看一下该类中重要的成员变量repoProject、manifestProject，都是MetaProject类的对象.
MetaProject类的代码如下
class MetaProject(Project):
"""A special project housed under .repo.
"""
def __init__(self, manifest, name, gitdir, worktree):
Project.__init__(self,
manifest=manifest,
name=name,
gitdir=gitdir,
objdir=gitdir,
worktree=worktree,
remote=RemoteSpec('origin'),
relpath='.repo/%s' % name,
revisionExpr='refs/heads/master',
revisionId=None,
groups=None)
成员变量如下：
- manifest:是XmlManifest类的对象
- name:创建新仓库的名字
- gitdir: .git仓库的绝对路径
- worktree:工作目录
- remote：远程仓库
- relpath：创建新仓库的相对于.repo目录的路径
- revisionExpr： 分支
MetaProject和Project对于仓库的操作逻辑差不多一样，不过为了体现这两个仓库（repo仓库和manifest仓库）在AOSP项目整个仓库集的重要性，才会有这样的命名。
Project类的代码如下：
class Project(object):
# These objects can be shared between several working trees.
shareable_files = ['description', 'info']
shareable_dirs = ['hooks', 'objects', 'rr-cache', 'svn']
# These objects can only be used by a single working tree.
working_tree_files = ['config', 'packed-refs', 'shallow']
working_tree_dirs = ['logs', 'refs']
def __init__(self,
manifest,
name,
remote,
gitdir,
objdir,
worktree,
relpath,
revisionExpr,
revisionId,
rebase=True,
groups=None,
sync_c=False,
sync_s=False,
clone_depth=None,
upstream=None,
parent=None,
is_derived=False,
dest_branch=None,
optimized_fetch=False,
old_revision=None):
"""Init a Project object.
Args:
manifest: The XmlManifest object.
name: The `name` attribute of manifest.xml's project element.
remote: RemoteSpec object specifying its remote's properties.
gitdir: Absolute path of git directory.
objdir: Absolute path of directory to store git objects.
worktree: Absolute path of git working tree.
relpath: Relative path of git working tree to repo's top directory.
revisionExpr: The `revision` attribute of manifest.xml's project element.
revisionId: git commit id for checking out.
rebase: The `rebase` attribute of manifest.xml's project element.
groups: The `groups` attribute of manifest.xml's project element.
sync_c: The `sync-c` attribute of manifest.xml's project element.
sync_s: The `sync-s` attribute of manifest.xml's project element.
upstream: The `upstream` attribute of manifest.xml's project element.
parent: The parent Project object.
is_derived: False if the project was explicitly defined in the manifest;
True if the project is a discovered submodule.
dest_branch: The branch to which to push changes for review by default.
optimized_fetch: If True, when a project is set to a sha1 revision, only
fetch from the remote if the sha1 is not present locally.
old_revision: saved git commit id for open GITC projects.
"""
self.manifest = manifest
self.name = name
self.remote = remote
self.gitdir = gitdir.replace('\\', '/')
self.objdir = objdir.replace('\\', '/')
if worktree:
self.worktree = worktree.replace('\\', '/')
else:
self.worktree = None
self.relpath = relpath
self.revisionExpr = revisionExpr
if revisionId is None \
and revisionExpr \
and IsId(revisionExpr):
self.revisionId = revisionExpr
else:
self.revisionId = revisionId
self.rebase = rebase
self.groups = groups
self.sync_c = sync_c
self.sync_s = sync_s
self.clone_depth = clone_depth
self.upstream = upstream
self.parent = parent
self.is_derived = is_derived
self.optimized_fetch = optimized_fetch
self.subprojects = []
self.snapshots = {}
self.copyfiles = []
self.linkfiles = []
self.annotations = []
self.config = GitConfig.ForRepository(
gitdir=self.gitdir,
defaults=self.manifest.globalConfig)
if self.worktree:
self.work_git = self._GitGetByExec(self, bare=False, gitdir=gitdir)
else:
self.work_git = None
self.bare_git = self._GitGetByExec(self, bare=True, gitdir=gitdir)
self.bare_ref = GitRefs(gitdir)
self.bare_objdir = self._GitGetByExec(self, bare=True, gitdir=objdir)
self.dest_branch = dest_branch
self.old_revision = old_revision
# This will be filled in if a project is later identified to be the
# project containing repo hooks.
self.enabled_repo_hooks = []
Project是用来描述AOSP项目某一个仓库（或者说项目）,其中有几个重要的值是来源于manifest.xml, name,revisionExpr,rebase,groups,sync_c,sync_s,upstream 这几个值对应到manifest.xml中某个标签的属性值，后续我们在克隆projects仓库集会讲解manifest标签和属性的用途。所以AOSP项目的仓库信息都在manifest.xml,除了repo仓库和manifest仓库，这些信息是在我们使用"repo sync"时会用到。
现在我们回到成员函数_Run的流程中，XmlManifest类已经构造完了。cmd.OptionParser.parse_args(argv) ,再去获取每个指令独有的OptionParser并且解析指令 init -u xxxx -b xxx
OptionParser属性函数的代码如下：
class Command(object):
"""Base class for any command line action in repo.
"""
...
@property
def OptionParser(self):
if self._optparse is None:
try:
me = 'repo %s' % self.NAME
usage = self.helpUsage.strip().replace('%prog', me)
except AttributeError:
usage = 'repo %s' % self.NAME
self._optparse = optparse.OptionParser(usage=usage)
self._Options(self._optparse)
return self._optparse
...
def _Options(self, p):
"""Initialize the option parser.
"""
Command的衍生类重写了基类的_Options，定义了属于自己的options,先留个坑后面讲到"repo sync"的时候再分析。
创建完XmlManifest类，解析命令行后，接下来就是调用Execute。
Command类是所有命令（init、sync、start）的基类，其成员函数Execute被其衍生类重写，故调用成员函数Execute就可以执行某个命令对应的成员函数Execute。所以，执行到这一行 result = cmd.Execute(copts, cargs) 的时候,就是整个架构的分水岭了。下面的图片是对前面的总结。
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-DjjGJA5V-1667225913433)({{site.baseurl}}/images/2017-04-12/2017-04-12-repo__Repo_Run_flowchart.png)]{:.white-bg-image}](https://img-blog.youkuaiyun.com/20170422193253305?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvaGF3a3M5Mw==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast)
接下来就是执行init模块中Init类的成员函数Execute：
class Init(InteractiveCommand, MirrorSafeCommand):
...
def Execute(self, opt, args):
git_require(MIN_GIT_VERSION, fail=True)
if opt.reference:
opt.reference = os.path.expanduser(opt.reference)
# Check this here, else manifest will be tagged "not new" and init won't be
# possible anymore without removing the .repo/manifests directory.
if opt.archive and opt.mirror:
...
sys.exit(1)
self._SyncManifest(opt)
self._LinkManifest(opt.manifest_name)
if os.isatty(0) and os.isatty(1) and not self.manifest.IsMirror:
if opt.config_name or self._ShouldConfigureUser():
self._ConfigureUser()
self._ConfigureColor()
self._ConfigureDepth(opt)
self._DisplayResult()
Init类的成员函数Execute的重点在于两个成员函数_SyncManifest和_LinkManifest，前者会克隆出manifest仓库并且切换到可用的分支上，后者会通过os模块symlink函数生成链接文件manifest.xml。
_SyncManifest函数的代码如下：
class Init(InteractiveCommand, MirrorSafeCommand):
...
def _SyncManifest(self, opt):
m = self.manifest.manifestProject
is_new = not m.Exists
if is_new:
...
m._InitGitDir(mirror_git=mirrored_manifest_git)
if opt.manifest_branch:
m.revisionExpr = opt.manifest_branch
else:
m.revisionExpr = 'refs/heads/master'
else:
if opt.manifest_branch:
m.revisionExpr = opt.manifest_branch
else:
m.PreSync()
...
if not m.Sync_NetworkHalf(is_new=is_new, quiet=opt.quiet,
clone_bundle=not opt.no_clone_bundle,
current_branch_only=opt.current_branch_only,
no_tags=opt.no_tags):
r = m.GetRemote(m.remote.name)
print('fatal: cannot obtain manifest %s' % r.url, file=sys.stderr)
# Better delete the manifest git dir if we created it; otherwise next
# time (when user fixes problems) we won't go through the "is_new" logic.
if is_new:
shutil.rmtree(m.gitdir)
sys.exit(1)
if opt.manifest_branch:
m.MetaBranchSwitch()
syncbuf = SyncBuffer(m.config)
m.Sync_LocalHalf(syncbuf)
syncbuf.Finish()
if is_new or m.CurrentBranch is None:
if not m.StartBranch('default'):
print('fatal: cannot create default in manifest', file=sys.stderr)
sys.exit(1)
Init类的成员函数_SyncManifest会克隆一个仓库，流程一般如下： git init--->git fetch--->git checkout branch_name 。对应的Project类成员函数就是_InitGitDir，Sync_NetworkHalf，Sync_LocalHalf,是不是很熟悉，跟克隆repo仓库的流程是一样的，其实repo仓库、manifest仓库、projects仓库集这些仓库克隆出来的方式是一样的。
class Project(object):
...
def _InitGitDir(self, mirror_git=None, force_sync=False):
init_git_dir = not os.path.exists(self.gitdir)
init_obj_dir = not os.path.exists(self.objdir)
try:
# Initialize the bare repository, which contains all of the objects.
if init_obj_dir:
os.makedirs(self.objdir)
self.bare_objdir.init()
...
_InitGitDir，初始化的仓库为manifest.git,manifest目录下的.git仓库是manifest的复制品，通过Project类的成员函数_InitWorkTree创建。接着再说类_GitGetByExec，GitGetByExec的对象bare_objdir封装了操作仓库的命令。比如git init。但是却找不到成员函数init，原来成员函数init是动态定义的。关键的地方就在于_GitGetByExec类的成员函数_getattr。
_GitGetByExec类的成员函数__getattr__代码如下:
class Project(object):
...
class _GitGetByExec(object):
...
def __getattr__(self, name):
...
name = name.replace('_', '-')
def runner(*args, **kwargs):
cmdv = []
config = kwargs.pop('config', None)
...
if config is not None:
if not git_require((1, 7, 2)):
...
for k, v in config.items():
cmdv.append('-c')
cmdv.append('%s=%s' % (k, v))
cmdv.append(name)
cmdv.extend(args)
p = GitCommand(self._project,
cmdv,
bare=self._bare,
gitdir=self._gitdir,
capture_stdout=True,
capture_stderr=True)
if p.Wait() != 0:
...
r = p.stdout
try:
r = r.decode('utf-8')
except AttributeError:
pass
if r.endswith('\n') and r.index('\n') == len(r) - 1:
return r[:-1]
return r
return runner
runner闭包用来处理调用者提供的参数，比如bare_git.describe(project.GetRevisionId())中的"project.GetRevisionId()",对应的git命令就是 git describe args
所以_GitGetByExec类通过成员函数__getattr__可以向工厂一样生产一些执行git命令的成员函数。既然仓库已经初始化好了，那么接下来就是fetch仓库了。
Sync_NetworkHalf成员函数的代码如下：
class Project(object):
...
def Sync_NetworkHalf(self,
quiet=False,
is_new=None,
current_branch_only=False,
force_sync=False,
clone_bundle=True,
no_tags=False,
archive=False,
optimized_fetch=False,
prune=False):
...
if (need_to_fetch and
not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir,
current_branch_only=current_branch_only,
no_tags=no_tags, prune=prune, depth=depth)):
return False
if self.worktree:
self._InitMRef()
else:
self._InitMirrorHead()
try:
os.remove(os.path.join(self.gitdir, 'FETCH_HEAD'))
except OSError:
pass
return True
Project类Sync_NetworkHalf方法调用_RemoteFetch方法实现了从远程仓库fetch记录到本地仓库，_RemoteFetch函数其实是"git fetch"命令的封装。
Sync_LocalHalf成员函数的代码如下：
class Project(object):
...
def Sync_LocalHalf(self, syncbuf, force_sync=False):
"""Perform only the local IO portion of the sync process.
Network access is not required.
"""
self._InitWorkTree(force_sync=force_sync)
...
revid = self.GetRevisionId(all_refs)
def _doff():
self._FastForward(revid)
self._CopyAndLinkFiles()
head = self.work_git.GetHead()
...
if branch is None or syncbuf.detach_head:
# Currently on a detached HEAD. The user is assumed to
# not have any local modifications worth worrying about.
#
...
if head == revid:
# No changes; don't do anything further.
# Except if the head needs to be detached
#
if not syncbuf.detach_head:
# The copy/linkfile config may have changed.
self._CopyAndLinkFiles()
return
else:
lost = self._revlist(not_rev(revid), HEAD)
if lost:
syncbuf.info(self, "discarding %d commits", len(lost))
try:
self._Checkout(revid, quiet=True)
except GitError as e:
syncbuf.fail(self, e)
return
self._CopyAndLinkFiles()
return
if head == revid:
# No changes; don't do anything further.
#
# The copy/linkfile config may have changed.
self._CopyAndLinkFiles()
return
branch = self.GetBranch(branch)
if not branch.LocalMerge:
# The current branch has no tracking configuration.
# Jump off it to a detached HEAD.
#
...
try:
self._Checkout(revid, quiet=True)
except GitError as e:
syncbuf.fail(self, e)
return
self._CopyAndLinkFiles()
return
upstream_gain = self._revlist(not_rev(HEAD), revid)
pub = self.WasPublished(branch.name, all_refs)
if pub:
not_merged = self._revlist(not_rev(revid), pub)
if not_merged:
...
return
elif pub == head:
# All published commits are merged, and thus we are a
# strict subset. We can fast-forward safely.
#
syncbuf.later1(self, _doff)
return
# Examine the local commits not in the remote. Find the
# last one attributed to this user, if any.
#
local_changes = self._revlist(not_rev(revid), HEAD, format='%H %ce')
last_mine = None
cnt_mine = 0
for commit in local_changes:
commit_id, committer_email = commit.decode('utf-8').split(' ', 1)
if committer_email == self.UserEmail:
last_mine = commit_id
cnt_mine += 1
if not upstream_gain and cnt_mine == len(local_changes):
return
...
branch.remote = self.GetRemote(self.remote.name)
if not ID_RE.match(self.revisionExpr):
# in case of manifest sync the revisionExpr might be a SHA1
branch.merge = self.revisionExpr
if not branch.merge.startswith('refs/'):
branch.merge = R_HEADS + branch.merge
branch.Save()
if cnt_mine > 0 and self.rebase:
def _dorebase():
self._Rebase(upstream='%s^1' % last_mine, onto=revid)
self._CopyAndLinkFiles()
syncbuf.later2(self, _dorebase)
elif local_changes:
try:
self._ResetHard(revid)
self._CopyAndLinkFiles()
except GitError as e:
syncbuf.fail(self, e)
return
else:
syncbuf.later1(self, _doff)
Project类的成员函数Sync_LocalHalf内部流程较为复杂，这里我们只讲checkout到一个干净的分支。
- _InitWorkTree成员函数：初始化manifest工作目录下的.git仓库
- _Checkout成员函数：通过"git checkout"切换分支。
_LinkManifest成员函数的代码如下：
class Init(InteractiveCommand, MirrorSafeCommand):
...
def _LinkManifest(self, name):
if not name:
print('fatal: manifest name (-m) is required.', file=sys.stderr)
sys.exit(1)
try:
self.manifest.Link(name)
except ManifestParseError as e:
print("fatal: manifest '%s' not available" % name, file=sys.stderr)
print('fatal: %s' % str(e), file=sys.stderr)
sys.exit(1)
成员函数_LinkManifest最终会调用os.symlink，创建manifest工作目录下default.xml的链接文件manifest.xml到 .repo目录下，这样方便访问manifest.xml文件
Projects仓库集
执行完repo init就获取到了repo仓库和manifest仓库了，接下来就要通过manifest.xml链接文件中的AOSP各个项目的元数据，获取projects仓库集。先来看看其内容：
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<remote name="aosp"
fetch=".."
review="https://android-review.googlesource.com/" />
<default revision="refs/tags/android-4.2_r1"
remote="aosp"
sync-j="4" />
<project path="build" name="platform/build" >
<copyfile src="core/root.mk" dest="Makefile" />
</project>
<project path="abi/cpp" name="platform/abi/cpp" />
<project path="bionic" name="platform/bionic" />
......
</manifest>
想了解更多的manifest.xml可以查看.repo/repo/docs/manifest-format.txt。这里我们只做简单了解
manifest.xml定义了四种标签：
- remote：该标签描述的是远程仓库信息。其中的fetch值相当于url路径的前缀。就好比
git@github.com:HawksJamesf/blog.git中的git@github.com:，标明了服务器。属性review用于code review服务器地址。 - default：属性revision表明了AOSP项目使用的开发分支，属性sync-j表明了拉取代码时使用的cpu核数
- project: 描述了相对于远程仓库的位置和相对于AOSP根目录的目录名字。比如想要获取build仓库，远程仓库的url为
https://android.googlesource.com/platform，那么该仓库的对应的远程仓库的url就是https://android.googlesource.com/platform/build - copyfile: 属性src为某个文件在远程仓库的位置，属性dest为本地仓库的位置。
执行 repo sync -j 8 命令行，流程就跟执行repo init是一样的，到了main模块里面的_Repo类的成员函数_Run调用cmd.Execute(copts, cargs)这个风水岭，才会执行属于sync模块的代码。但是关于copts，cargs参数的如何获取，我们还得先看cmd.OptionParser.parse_args(argv)。
_Options成员函数的代码如下：
class Sync(Command, MirrorSafeCommand):
...
def _Options(self, p, show_smart=True):
try:
self.jobs = self.manifest.default.sync_j
except ManifestParseError:
self.jobs = 1
...
p.add_option('-l', '--local-only',
dest='local_only', action='store_true',
help="only update working tree, don't fetch")
p.add_option('-n', '--network-only',
dest='network_only', action='store_true',
help="fetch only, don't update working tree")
...
p.add_option('-m', '--manifest-name',
dest='manifest_name',
help='temporary manifest to use for this sync', metavar='NAME.xml')
...
p.add_option('-u', '--manifest-server-username', action='store',
dest='manifest_server_username',
help='username to authenticate with the manifest server')
p.add_option('-p', '--manifest-server-password', action='store',
dest='manifest_server_password',
help='password to authenticate with the manifest server')
p.add_option('--fetch-submodules',
dest='fetch_submodules', action='store_true',
help='fetch submodules from server')
...
if show_smart:
p.add_option('-s', '--smart-sync',
dest='smart_sync', action='store_true',
help='smart sync using manifest from the latest known good build')
p.add_option('-t', '--smart-tag',
dest='smart_tag', action='store',
help='smart sync using manifest from a known tag')
g = p.add_option_group('repo Version options')
g.add_option('--no-repo-verify',
dest='no_repo_verify', action='store_true',
help='do not verify repo source code')
g.add_option('--repo-upgraded',
dest='repo_upgraded', action='store_true',
help=SUPPRESS_HELP)
在分析repo init时已经说用，Command的衍生类override成员函数_Options，才能得到独有的OptionParser。还记得 repo command line --->optparse--->git command line这个流程吗 ? 每种命令都有其对应的OptionParser，这样才能做到各个命令模块有自己处理repo command line的逻辑。紧接着把解析后的值传给成员函数Execute。
Execute成员函数的代码如下：
class Sync(Command, MirrorSafeCommand):
...
def Execute(self, opt, args):
...
manifest_name = opt.manifest_name
...
rp = self.manifest.repoProject
rp.PreSync()
mp = self.manifest.manifestProject
mp.PreSync()
...
if not opt.local_only:
mp.Sync_NetworkHalf(quiet=opt.quiet,
current_branch_only=opt.current_branch_only,
no_tags=opt.no_tags,
optimized_fetch=opt.optimized_fetch)
if mp.HasChanges:
syncbuf = SyncBuffer(mp.config)
mp.Sync_LocalHalf(syncbuf)
if not syncbuf.Finish():
sys.exit(1)
self._ReloadManifest(manifest_name)
if opt.jobs is None:
self.jobs = self.manifest.default.sync_j
...
all_projects = self.GetProjects(args,
missing_ok=True,
submodules_ok=opt.fetch_submodules)
self._fetch_times = _FetchTimes(self.manifest)
if not opt.local_only:
to_fetch = []
now = time.time()
if _ONE_DAY_S <= (now - rp.LastFetch):
to_fetch.append(rp)
to_fetch.extend(all_projects)
to_fetch.sort(key=self._fetch_times.Get, reverse=True)
fetched = self._Fetch(to_fetch, opt)
_PostRepoFetch(rp, opt.no_repo_verify)
if opt.network_only:
# bail out now; the rest touches the working tree
return
# Iteratively fetch missing and/or nested unregistered submodules
previously_missing_set = set()
while True:
...
all_projects = self.GetProjects(args,
missing_ok=True,
submodules_ok=opt.fetch_submodules)
missing = []
for project in all_projects:
if project.gitdir not in fetched:
missing.append(project)
if not missing:
break
# Stop us from non-stopped fetching actually-missing repos: If set of
# missing repos has not been changed from last fetch, we break.
missing_set = set(p.name for p in missing)
if previously_missing_set == missing_set:
break
previously_missing_set = missing_set
fetched.update(self._Fetch(missing, opt))
...
if self.UpdateProjectList():
sys.exit(1)
...
for project in all_projects:
...
if project.worktree:
project.Sync_LocalHalf(syncbuf, force_sync=opt.force_sync)
...
...
前期会有一些更新检查repo仓库和manifest仓库的工作，后期就会拉去projects仓库集，那么下面我们就来粗糙的理解执行成员函数Execute的流程：
- 一开始获取manifest仓库和repo仓库的对象，然后都会调用之前分析过的PreSync，如果opt.local_only不存在，就会调用Sync_NetworkHalf成员函数更新manifest仓库。紧接着如果manifest本地仓库相对于远程仓库有变化，就会调用Sync_LocalHalf做一些merge或者rebase操作，然后调用ReloadManifest成员函数重新从manifest.xml载入数据到对象。
- 接下来就是_Fetch成员函数，其中除了manifest仓库，其他的仓库都会更新。如果开启的合数大于1的话就会创建新的线程，防止主线程阻塞，其中关于线程同步机制可以查看这里。而获取projects仓库集，主要使用的是Project类的成员函数Sync_NetworkHalf，接着调用_PostRepoFetch函数判断repo仓库是否有变化，如果是，则调用Sync_LocalHalf成员函数做一些merge或者rebase操作。
- 紧接着通过GetProjects成员函数从 .repo/projects目录下得到AOSP所有仓库对象的列表，不包括repo仓库和manifest仓库，这样就可以调用Sync_LocalHalf成员函数。如果参数args指定了具体的仓库（即repo sync project_name），那么GetProjects成员函数就只能得到指定的仓库。获取仓库的方式有两种：一种_GetProjectByPath，另一种是GetProjectsWithName。
至此，repo仓库、manifest仓库、projects仓库集连同其对应的工作目录都已经初始化完成。那么是不是就可以开始开发呢 ？ 其实接下来还要为AOSP项目的仓库创建一个新的开发分支，只有这样我们才能够在分支上面提交、上传自己的代码。也只有这样当我们发布了一个版本就可以给这个版本打上一个tag。当项目可以量产时，就可以在这个分支基础上创建出一个量产分支，并上传到服务器。
创建分支
repo start master --all 其实挺好理解这个命令行的，就是 git checkout -b name 命令行的批量操作。留个坑，以后填吧。
class Start(Command):
...
def _Options(self, p):
p.add_option('--all',
dest='all', action='store_true',
help='begin branch in all projects')
def Execute(self, opt, args):
if not args:
self.Usage()
nb = args[0]
if not git.check_ref_format('heads/%s' % nb):
print("error: '%s' is not a valid name" % nb, file=sys.stderr)
sys.exit(1)
err = []
projects = []
if not opt.all:
projects = args[1:]
if len(projects) < 1:
projects = ['.',] # start it in the local project by default
all_projects = self.GetProjects(projects,
missing_ok=bool(self.gitc_manifest))
# This must happen after we find all_projects, since GetProjects may need
# the local directory, which will disappear once we save the GITC manifest.
if self.gitc_manifest:
gitc_projects = self.GetProjects(projects, manifest=self.gitc_manifest,
missing_ok=True)
for project in gitc_projects:
if project.old_revision:
project.already_synced = True
else:
project.already_synced = False
project.old_revision = project.revisionExpr
project.revisionExpr = None
# Save the GITC manifest.
gitc_utils.save_manifest(self.gitc_manifest)
# Make sure we have a valid CWD
if not os.path.exists(os.getcwd()):
os.chdir(self.manifest.topdir)
pm = Progress('Starting %s' % nb, len(all_projects))
for project in all_projects:
pm.update()
if self.gitc_manifest:
gitc_project = self.gitc_manifest.paths[project.relpath]
# Sync projects that have not been opened.
if not gitc_project.already_synced:
proj_localdir = os.path.join(self.gitc_manifest.gitc_client_dir,
project.relpath)
project.worktree = proj_localdir
if not os.path.exists(proj_localdir):
os.makedirs(proj_localdir)
project.Sync_NetworkHalf()
sync_buf = SyncBuffer(self.manifest.manifestProject.config)
project.Sync_LocalHalf(sync_buf)
project.revisionId = gitc_project.old_revision
# If the current revision is a specific SHA1 then we can't push back
# to it; so substitute with dest_branch if defined, or with manifest
# default revision instead.
branch_merge = ''
if IsId(project.revisionExpr):
if project.dest_branch:
branch_merge = project.dest_branch
else:
branch_merge = self.manifest.default.revisionExpr
if not project.StartBranch(nb, branch_merge=branch_merge):
err.append(project)
pm.end()
if err:
for p in err:
print("error: %s/: cannot start %s" % (p.relpath, nb),
file=sys.stderr)
sys.exit(1)
参考资料
Android Open Source Project
repo仓库源码
清华大学提供的AOSP
Android源代码仓库及其管理工具Repo分析
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