Note that Simon Marlow had submitted a patch around 2004 that added hard link
support, but it turned out to be a bit overzealous.  The patch in question
modified the code which is used by darcs optimize --relink (I think) and was
overly optimistic about determining if two files really were the same and could
be replaced by a hard link.

On the other hand, there are cases where darcs /knows/ it wants a hardlink, and
if the underlying filesystem supports them -- apparently NTFS does -- we should
have them

I guess this should be assigned to Salvatore?

Salvatore, would you be interested in taking this on?  I hope finding the patch
won't be too difficult.

The following patch updated the status of issue1173 to be resolved:

* Resolve issue1173: support hard links on NTFS. 
Ignore-this: 1180c0031c5e689c431ab7b0ac29d344

There are some limitations:
- I didn't modify maybe_relink.c, so it doesn't work in darcs optimize --relink.
- It works breaks compatibility on Windows versions before Windows 2000.
- It works only on NTFS, but fails gracefully.