本地添加Git子模块失败求助：file协议受限及SSH分支报错

需要在islandpk仓库中将本地yoken包部署到src/yoken路径，作为Git子模块使用以获取本地Python包的使用权限，但多次尝试均失败，以下是具体尝试过程及报错：

尝试1：直接使用本地绝对路径 #

执行命令：

git submodule add /Users/hecate/Applications/persephone-python-pac/src/yoken ./src/yoken

报错：

Cloning into '/Users/hecate/Applications/islandpk/src/yoken'...
fatal: transport 'file' not allowed
fatal: clone of '/Users/hecate/Applications/persephone-python-pac/src/yoken' into submodule path '/Users/hecate/Applications/islandpk/src/yoken' failed

尝试2：使用file://协议 #

执行命令：

git submodule add file:///Users/hecate/Applications/persephone-python-pac/src/yoken ./src/yoken

报错：

Cloning into '/Users/hecate/Applications/islandpk/src/yoken'...
fatal: transport 'file' not allowed
fatal: clone of 'file:///Users/hecate/Applications/persephone-python-pac/src/yoken' into submodule path '/Users/hecate/Applications/islandpk/src/yoken' failed

尝试3：使用相对路径 #

执行命令：

git submodule add ../persephone-python-pac/src/yoken src/yoken

报错：

Cloning into '/Users/hecate/Applications/islandpk/src/yoken'...
fatal: transport 'file' not allowed
fatal: clone of '/Users/hecate/Applications/persephone-python-pac/src/yoken' into submodule path '/Users/hecate/Applications/islandpk/src/yoken' failed

尝试4：改用本地裸仓库 #

先后执行以下命令，均出现相同报错：

git submodule add file:///Users/hecate/.git-repos/yoken/ src/yoken

git submodule add /Users/hecate/.git-repos/yoken/ src/yoken 

git submodule add -- /Users/hecate/.git-repos/yoken/ src/yoken

报错：

Cloning into '/Users/hecate/Applications/islandpk/src/yoken'...
fatal: transport 'file' not allowed
fatal: clone of '[对应仓库路径]' into submodule path '/Users/hecate/Applications/islandpk/src/yoken' failed

尝试5：改用远程SSH仓库 #

执行命令：

git submodule add ssh://xxxx:/home/rand_usr/.git-repos/yoken ./src/yoken

执行过程及报错：

Cloning into '/Users/hecate/Applications/islandpk/src/yoken'...
rand_usr@xx.xx.x.xx's password: 
remote: Counting objects: 7, done.
remote: Compressing objects: 100% (6/6), done.
remote: Total 7 (delta 1), reused 0 (delta 0)
Receiving objects: 100% (7/7), done.
Resolving deltas: 100% (1/1), done.
fatal: You are on a branch yet to be born
fatal: unable to checkout submodule 'src/yoken'

内容的提问来源于stack exchange，提问作者croakouttatune