[Haskell-cafe] Why does cabal sdist still make tarballs with incorrect file modes?

As I played with GHC 7.0.1, I noticed that Cabal sdist is still hosed. Since ten months ago, cabal sdist fails to preserve the file mode bits of the source files put into the tarball being generated (Ticket #627 reported by draconx). An executable shell script and a source file world readable both have a mode of 600 in the tarball. Does anyone know why this bug is difficult to fix? Why can't one revert to the code used in Cabal 1.6.0.1, which is know to work? John