win32: remove useless lstat() fallback in nlinks()
The fallback was introduced by
3b4f05ff3130 at the same time than
nlinks(). Apparently it only handles the case where target path
does not exist. Just raise IOError directly.
win32: correctly break hardlinks on network drives (
issue761)
win32.nlinks() was often returning 1 instead of the correct
hardlinks count when reading from network drives. This made
commit or push to a repository on a network share to fail
breaking the hardlinks in the datastore, possibly causing
integrity errors in repositories linked locally on the remote
side.
Here is what the MSDN says about GetFileInformationByHandle():
Depending on the underlying network features of the operating
system and the type of server connected to, the
GetFileInformationByHandle function may fail, return partial
information, or full information for the given file.
In practice, we never got the correct hardlinks count when
reading from and to many combinations of Window XP, 2003, Vista
and 7, via network drives or RDP shares. It always returned 1
instead. The only setup returning an accurate links count was a
samba on Debian.
To avoid this, Mercurial now breaks the hardlinks unconditionally
when writing to a network drive.