I'm going to guess that I know the answer already.
I have a friend who wants to collaborate on a pro-bono site I am developing. So I thought of creating a repository on GitHub to make it easier. But I do all my development in a true multisite (single code base). So, for example, sites/all/modules contains every module that any of my sites uses. This is far more than this particular site uses.
If I build a repository, is it not going to contain all those modules (themes, images, etc) even though they are not needed for this site? Do I need to split it off to a single site with only the modules (etc.) that are needed for that one site?
I think building and maintaining a .gitignore file would be far more annoying than splitting the site.
Nancy Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.