darcs diff is looking for more files than it ought:

: nr@yorkie 5596 ; darcs diff --from-patch='ghctags compile again' GhcTags.hs
darcs: ./compiler/nativeGen/SPARC/CodeGen/Gen32.hs: openBinaryFile: does not exist (No such file or directory)

You can reproduce this with the current HEAD of GHC, in directory 
utils/ghctags.

I suspect it may be opening every file mentioned in every patch.
It should obviously not fall over if a file is mentioned in a patch
but no longer exists.

Also to the point, since I've asked for one particular file
on the command line, there's no reason darcs should ask for
anything  not identical to that file (or related to it by darcs mv).

Norman

P.S. dunno if 678 is related---couldn't find much useful with a search.

Could I get a volunteer to build a minimal test case for this?

Norman, if it won't be too much trouble for you: 
http://wiki.darcs.net/index.html/RegressionTests

Otherwise, any takers?

Eric,

I'd love to help, but my plate is way too full and will remain that
way at least until July 15 (the POPL deadline).

Norman

Hi Norman,

So I think this is really two bugs in one.  I've split off the bit about not
looking at unnecessary files into issue1600.

Meanwhile, for the error, I ran
$ darcs diff --from-patch='ghctags compile again' GhcTags.hs
in ghctags of a GHC repo whose latest patch is from 2009-04 and did not get any
error messages.

By any chance was this a partial repository?

If so, I think what will most likely happen is that we will retire support for
partial repositories before we fix the bug.

Thanks for the bug report!