[GHC] #9322: Modify readProcess[WithExitCode] to allow setting current directory

[GHC]

#9322: Modify readProcess[WithExitCode] to allow setting current directory
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        Reporter:  blitzcode         |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:  7.10.1
       Component:                    |                 Version:  7.8.3
  libraries/process                  |  Differential Revisions:
        Keywords:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  None/Unknown      |              Difficulty:  Easy (less
       Test Case:                    |  than 1 hour)
        Blocking:                    |              Blocked By:
                                     |         Related Tickets:
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 The readProcess[WithExitCode] function does not allow to modify the
 working directory parameter passed to createProcess.

 The documentation states 'readProcess and readProcessWithExitCode are
 fairly simple wrappers around createProcess. Constructing variants of
 these functions is quite easy'. I would call that a boldfaced lie, as the
 implementation of readProcess[WithExitCode] and its web of required,
 hidden helper functions spans multiple screen pages of subtle and error
 prone code. Just look at the numerous bug reports for it. It would seem
 rather unfortunate to extract and copy paste all of this from
 System.Process just to provide a working directory to a newly created
 process.

 Maybe the call should be changed to simply specify a default CreateProcess
 record so all things like cwd/env could be customized?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9322>
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