Krasimir says:
  Small fixes in the parser/printer. When there is a package description with
  executables only then the old implementation of pretty printer was written
  to print empty "exposed-modules" field while there isn`t any library. After
  that the parser will generate PackageDescription with (Just emptyLibrary)
  instead of Nothing. Now exposed-modules field is printed only if
  library /= Nothing

Ross says:
  In smartCopySources, don't try to strip the prefix if it was ".",
  because joinFileName "." x == x
  (fixes bug reported by Iavor Diatchki)

  Improve sdist a bit: copy files named in main-is, license-file and c-sources.
  Also supply a default Setup.hs if none is present.
  
  This will get it working for only the simplest of packages.  It omits
  header files, configure stuff and files named in the buildinfo file.
  To do it properly, we'd need a field in the package description listing
  extra files to copy into a source distribution.