When pulling to a mounted Samba (cifs) directory, the directory is left with
temporary files and a temporary directory called "darcs_testing_nfs".

I've confirmed this in the sense that I see references to
"darcs_testing_for_nfs" in src/Darcs/CheckFileSystem.lhs, and I see that the
file hasn't changed since this bug was reported. I suspect the issue still exists.

I'm not sure.  We need someone with a samba directory to test this.

Some comments by Grant Husbands: 
> We use Darcs over samba (always windows on at least one side, and            
                                                     
> mostly linux on the other side) all the time (since SSH used to be very      
                                                          
> slow) and have never seen a darcs_testing_nfs file or such. There seem       
                                                          
> to be no such files on our primary (linux) samba share for Darcs repos.

Here's the relevant bit of code that Mark was looking at:

can_I_use_mmap :: IO Bool
can_I_use_mmap = do a <- can_I_remove_open_files
                    if a then can_I_remove_directories_holding_open_files
                         else return False

can_I_remove_directories_holding_open_files :: IO Bool
can_I_remove_directories_holding_open_files = block $
   (do createDirectory "darcs_testing_for_nfs"
       okay <- (withCurrentDirectory "darcs_testing_for_nfs" $
                do withOpenTemp $ \ (_,f) -> 
                       (do removeFile f
                           setCurrentDirectory ".."
                           removeDirectory "darcs_testing_for_nfs"
                           return True
                       ) `catch` \_ -> return False
               ) `catch` \_ -> return True
       removeDirectory "darcs_testing_for_nfs" `catch` \_ -> return ()
       return okay
   ) `catch` \_ -> return True

This code confuses me, but I think somebody else could use it to explain why
exactly this happens.

So we create darcs_testing_nfs, dump a temp file in it, then try to remove the
(open) temp file and the directory.  What's failing and what's being caught?

David (Waern): perhaps you might be interested in playing with this module a bit
and seeing what happens?  If not, maybe Grant/Edwin can shed more light on what
is (supposed to be) happening?