As reported in patch2344, the pattern
matches dist-newstyle/ on Linux, but not on Windows/Mac,
i.e. darcs wh -l reports that the folder is new on Windows/Mac
when it shouldn't.
I'll write a test, just creating the issue now so I have a name to give
After spending a while writing a test for this and getting a bit confused,
I finally realised that it is working fine in HEAD (i.e. screened)
but not with the 2.16 binary I was running with by default.
I'm not going to bother tracking down whatever fixed it.