[Hackage] #947: let "cabal -fSomeFlag" produce error for undeclared flags

[Hackage]

#947: let "cabal -fSomeFlag" produce error for undeclared flags
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  Reporter:  Oblosys             |        Owner:          
      Type:  enhancement         |       Status:  new     
  Priority:  normal              |    Milestone:          
 Component:  cabal-install tool  |      Version:  1.10.2.0
  Severity:  normal              |     Keywords:          
Difficulty:  unknown             |   Ghcversion:          
  Platform:                      |  
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 Typos in flags can lead to confusing problems, especially with large
 projects that take a long time to build. A simple check could be quite
 useful:

 ~> hconfigure -fNonExistentFlag -fSomeFlag
 cabal: undeclared flag 'NonExistentFlag'. Declared flags are:
   ExistentFlag, SomeFlag

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Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/947>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects