Setup repository with custom --git-dir

This feature should be pretty easy to implement, maybe a text box in repository setup?

Why such feature?
Most of time I'm working with some project repository in which I have other files generated by my IDE which I can not commit to this repo (other people might not be interested in those files).

In order to save those project's IDE settings I create another repository inside same directory but with different --git-dir for example ".git_IDE". In a fact this setup is two separate repository in one common directory.
I use SmartGit to work with the project but when I want to save the settings file I switch to command line and do for example:
git --git-dir=git_IDE add ide_settings
git --git-dir=git_IDE commit -a
git --git-dir=git_IDE push

It would be nice to have option in SmartGit to select defaul --git-dir per repository.