[Hackage] #376: Allow constraint on using installed package versions

[Hackage]

#376: Allow constraint on using installed package versions
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  Reporter:  duncan              |        Owner:       
      Type:  enhancement         |       Status:  new  
  Priority:  normal              |    Milestone:       
 Component:  cabal-install tool  |      Version:  HEAD 
  Severity:  normal              |     Keywords:       
Difficulty:  normal              |   Ghcversion:  6.8.3
  Platform:                      |  
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 We allow command line args for adding version constraints. Internally the
 dependency resolver can use constraints on the installed status. We should
 allow such constraints to be given on the command line, and possibly in
 the cabal config file.

 We should probably also allow preferences to be given on the command line
 too.

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Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/376>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects