1). 检查子目录.git/hook下面是否有 commit-msg 文件，
https://gerrit-review.googlesource.com/tools/hooks/commit-msg
2). 如果是repo sync 下来的代码，，只要检查子目录中是否存在 commit-msg 如果不存在，修改工程目录下面 .repo/manifest.xml，添加review项指定即可。
< remote name="origin" fetch=".." review="xxx.git/gerrit" />
注意必须添加上面的 review=”review.source.android.com” 这句。
在.repo/repo/project.py中，有这么一段代码：
def _InitHooks(self):hooks = os.path.realpath(self._gitdir_path('hooks'))if not os.path.exists(hooks):os.makedirs(hooks)for <span style="color:#FF0000;">stock_hook</span> in _ProjectHooks():name = os.path.basename(stock_hook)if name in ('commit-msg',) and not self.remote.review \and not self is self.manifest.manifestProject:# Don't install a Gerrit Code Review hook if this# project does not appear to use it for reviews.## Since the manifest project is one of those, but also# managed through gerrit, it's excludedcontinuedst = os.path.join(hooks, name)if os.path.islink(dst):continueif os.path.exists(dst):if filecmp.cmp(stock_hook, dst, shallow=False):os.remove(dst)else:_error("%s: Not replacing %s hook", self.relpath, name)continuetry:os.symlink(os.path.relpath(stock_hook, os.path.dirname(dst)), dst)except OSError as e:if e.errno == errno.EPERM:raise GitError('filesystem must support symlinks')else:raise什么是_ProjectHooks呢， def _ProjectHooks(): """List the hooks present in the 'hooks' directory. These hooks are project hooks and are copied to the '.git/hooks' directory of all subprojects. This function caches the list of hooks (based on the contents of the 'repo/hooks' directory) on the first call. Returns: A list of absolute paths to all of the files in the hooks directory. """ global _project_hook_list if _project_hook_list is None: d = os.path.realpath(os.path.abspath(os.path.dirname(__file__))) d = os.path.join(d , 'hooks') _project_hook_list = [os.path.join(d, x) for x in os.listdir(d)] return _project_hook_list具体来讲它列举.repo/hooks下的文件，让我们ls一下这个目录
ls hooks/commit-msg pre-auto-gc所以如果用gerrit的话，会把这两个hooks拷贝到对应子项目的.git/hooks下面，这样子你自己在每个子目录下commit代码的时候，都会自动帮你添加Changed-id了。
有多远，走多远，把足迹连成生命线。
