CWD is a useful concept. If I run gimp in a particular directory, I'd like it to show that directory in the file dialogue when I try to load or save an image.
What is evil is a program changing its working directory. That's when it becomes an evil global variable, rather than a non-evil global constant.
I think that's probably the best way to look at it. You are given the parent node with CWD and you can attempt to modify child nodes by relatively addressing them.
I was wondering before if it would be interesting to have a filesystem with transactional locking of paths, though I'm sure the performance would take a hit. Would be kind of cool to be able to do filesystem operations without constantly opening yourself up to race conditions and requiring extremely defensive programming.
Why limit that to one directory? As I expanded on a bit in my response to ygra, I don't mean eliminating any notion of carrying a directory, just that I don't know that there is actually good reason to privilege one particular path universally.
I agree that treating cwd as a global constant solves most (at least) of the issues, I'm just poking assumptions to see what ideas arise.
What is evil is a program changing its working directory. That's when it becomes an evil global variable, rather than a non-evil global constant.