[GHC] #2330: ghc-pkg should not report duplicate depends

[GHC]

#2330: ghc-pkg should not report duplicate depends
------------------------+---------------------------------------------------
    Reporter:  duncan   |       Owner:          
        Type:  bug      |      Status:  new     
    Priority:  normal   |   Component:  Compiler
     Version:  6.8.2    |    Severity:  normal  
    Keywords:           |    Testcase:          
Architecture:  Unknown  |          Os:  Unknown 
------------------------+---------------------------------------------------
 {{{
 $ ghc-pkg field regex-base-0.72.0.1 depends
 depends: base-3.0.1.0 array-0.1.0.0 base-3.0.1.0 bytestring-0.9.0.1
 }}}

 Note the `base-3.0.1.0 base-3.0.1.0`. This is clearly silly. It causes
 problems for Cabal. Although we can easily work around this using nub it'd
 be better if duplicate depends were never reported or better yet rejected
 or eliminated at package registration time.

 (I'm not sure how it ended up this way, I don't think Cabal makes package
 registration files with duplicate depends)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2330>
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