Support for submodules

[ki82]

Grgit fails to open submodules with "repository not found:", since there is no .git directory in a submodule.

In a submodule there is an .git file that in my example looks like this:
gitdir: ../.git/modules/subModuleFolder
If I use Grgit.open(' ../.git/modules/subModuleFolder') it seems to work fine.

It would be nice if grgit could internally read .git file in a submodule and then parse which git directory to use.

[ki82]

200$ is up for grabs for solving this at: https://freedomsponsors.org/issue/730/support-for-submodules

[ajoberstar]

Have you tried any of the new options introduced in 1.3.0? These fixed #64 and #66, which may be similar to the issue you're having.

[ki82]

Thanks, it worked by using the currentDir option