submodule path with symlinks

[Kyle Marek <psppsn96@gmail.com>]

Hello,

I've just hit this change in behavior introduced ~2 years ago, where 
submodule paths are no longer allowed to contain symlinks [1].

This change has broken a practice that I have used repeatedly over the 
years, where several worktrees share the same copy of their submodules. 
It has been very useful for project organization, but no longer works on 
updated systems for "security" reasons. Please, I understand the risks 
associated with symlinks, I do not want to be "protected from myself", 
and I do not want to re-architect affected projects.

I see there is even a TODO comment about exactly this issue [2]:

 > TODO: allow exempting it via `safe.submodule.path` or something

I'm surprised to see that this change went through without an 
accompanying commit to allowing exceptions or allowing the user accept 
the risks associated with symlinks.

Is there interest in implementing the TODO? Will you accept a patch for 
this?

Thank you,
Kyle Marek

[1]: https://git.kernel.org/pub/scm/git/git.git/commit/?id=e8d0608944486019ea0e1ed2ed29776811a565c2

[2]: https://git.kernel.org/pub/scm/git/git.git/tree/builtin/submodule--helper.c?id=e8d0608944486019ea0e1ed2ed29776811a565c2#n2679