limiting relationship of git dir and worktree (was Re: [PATCH] Support "core.excludesfile = ~/.gitignore")

> Judging from the occasional "I tried core.worktree but it does not work in
> this and that situations" I see here and on #git, my impression is that
> new people try it, saying "git is cool -- unlike cvs that sprinkles those
> ugly CVS directories all over the place, it only contaminates my work tree
> with a single directory '.git' and nothing else.  Ah, wait --- what's this
> core.worktree thing?  Can I get rid of that last one as well?  That sounds
> even cooler".
> 
> IOW, I do not think it is really _needed_ per-se as a feature, but it was
> done because it was thought to be doable, which unfortunately turned out
> to involve hair-pulling complexity that the two attempts that led to the
> current code still haven't resolved.
> 
> I really wish we do not have to worry about that anymore.