[Hackage] #246: cabal-install's tar unpacking does not cope well with links

[Hackage]

#246: cabal-install's tar unpacking does not cope well with links
----------------------------------+-----------------------------------------
  Reporter:  duncan               |        Owner:         
      Type:  defect               |       Status:  new    
  Priority:  normal               |    Milestone:         
 Component:  cabal-install tool   |      Version:  1.2.3.0
  Severity:  normal               |     Keywords:         
Difficulty:  very easy (<1 hour)  |   Ghcversion:  6.8.2  
  Platform:                       |  
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 {{{
 Extracting
 /home/me/.cabal/packages/hackage.haskell.org/pandoc/0.46/pandoc-0.46.tar.gz
 to /tmp/TMPpandoc-0.46...
 cabal: /tmp/TMPpandoc-0.46/pandoc-0.46/COPYRIGHT: copyFile: does not exist
 (No such file or directory)
 }}}

 If we look at this tarfile we find that the `COPYRIGHT` entry in the tar
 file is actually a symbolic link to `debian/copyright`. The tar code in
 `cabal-install` is designed to cope with symbolic links. It handles them
 by copying the target file. Same goes for hard links. The problem in this
 case is that it is trying to copy the other file before it has been
 unpacked.

 One partial solution would be to accumulate a list of links and then copy
 all at the end after the other files have been unpacked. It's only partial
 because someone could make a tarball with links pointing to other links.
 We can probably just ignore that problem and let it fail in the same way
 it does now.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/246>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects