[GHC] #9259: GHCi should list its available command line options

[GHC]

#9259: GHCi should list its available command line options
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              Reporter:  jstolarek   |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:
             Component:  Driver      |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by kolmodin):

 Making `--interactive` and `--show-options` work together is simple, just
 a few more lines to `setMode`.
 The time consuming part with this task is to cleanly separate which flags
 work in GHC and which work in GHCi.
 The flags are defined in a few different places;
  * `ModeFlags` defined in `ghc/Main.hs` which apply to both GHC and GHCi.
  * `StaticFlags` defined in `compiler/main/StaticFlags.hs` which applies
 to both GHC and GHCi.
  * DynFlags defined in `compiler/main/DynFlags.hs`. There are a few
 different kinds of flags here (dynflags, package flags, fflags, fwarn,
 ...), each of which where some are for GHC and some for GHCi. For some
 flags there is code guarding to make sure you don't mix them, like
 together with `--interactive` you cannot use `-prof`, `-threaded`,
 `-unreg`, `-debug` or `-ticky`. For other flags there is no such code, and
 it's not always obvious where each flag has effect.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9259#comment:3>
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