Subrepositories location

[J.S. van Bethlehem]

Hello hg-people,

Let me first say how happy I am with HG. I've been using basic HG for 
quite some while now and it suits all my needs.
So today I started experimenting a bit with the subrepo feature. And I 
have the following question:
is the location of a subrepo in some limited?

I have the following in my .hgsub file:
  bool = ../bool

It's kind of weird, I know, but that's the way it is. So I have some 
repository that should become the subrepo that is at the same level as 
the current repo. Now when I did hg ci, indeed I got a message that it 
was first comitting ../bool before comitting the current repo. Yet, when 
going to ../bool I saw that nothing had happened! So: is there some 
limitation on the type of relative paths that is accepted as subrepo? 
(eg: any subrepo for which the path starts with ../ is simply not allowed?)

Yours sincerely,
Jakob van Bethlehem