使用tag检出git submodule

背景

某个git库的gitmodules 文件如下：

[submodule "module1"]
    path = path1
    url = http://github.cn/module1.git
    branch = module1
[submodule "module2"]
    path = path2
    url = http://github.cn/module2.git
    tag = tag2
[submodule "module3"]
    path = path3
    url = http://github.cn/module3.git
    branch = module3

需要git module 检出的时候把module2 检出到tag2

解决

git submodule foreach  --recursive 'tag="$(git config -f $toplevel/.gitmodules submodule.$name.tag)";[[ -n $tag ]] && git reset --hard  $tag || echo "this module has no tag"'

foreach [--recursive] 
Evaluates an arbitrary shell command in each checked out submodule. 
The command has access to the variables $name, $sm_path, $displaypath, $sha1 and $toplevel: 
$name is the name of the relevant submodule section in .gitmodules, 
$sm_path is the path of the submodule as recorded in the immediate superproject, 
$displaypath contains the relative path from the current working directory to the submodules root directory, 
$sha1 is the commit as recorded in the immediate superproject, 
and $toplevel is the absolute path to the top-level of the immediate superproject. 
Note that to avoid conflicts with $PATH on Windows, the $path variable is now a deprecated synonym of $sm_path variable.
Any submodules defined in the superproject but not checked out are ignored by this command. 
Unless given --quiet, foreach prints the name of each submodule before evaluating the command. 
If --recursive is given, submodules are traversed recursively (i.e. the given shell command is evaluated in nested submodules as well). 
A non-zero return from the command in any submodule causes the processing to terminate. 
This can be overridden by adding || : to the end of the command.

As an example, the command below will show the path and currently checked out commit for each submodule:

git submodule foreach 'echo $path `git rev-parse HEAD`'

参考链接：
https://git-scm.com/docs/git-submodule