dirstate2 comments

[Robert Collins]

I'm not looking at this in any detail till next week, to keep to my
1-day-a-week-ish background priority on it; but let me just mention
that we need to design to the lowest set of facilities: if some FS's
can be better, and we can detect them at runtime, we can do better;
but for all those that can't, we need a base behaviour that works.

Things like NFS mounted volumes to a NTFS backend do arise, and will
pretty much guarantee that the default behaviour of rename on a FS is
all we can depend upon, when assessing the available-everywhere
facilities.

So specifically, we can't safely design around having:
 - transactional NTFS http://en.wikipedia.org/wiki/Transactional_NTFS
(not to mention, you need vista/server 2k8).
 - rename of open files

-Rob