[GHC] #16253: Offer a shorthand for `--skip=_build/stage$n/compiler/.dependencies.mk`

[GHC]

#16253: Offer a shorthand for `--skip=_build/stage$n/compiler/.dependencies.mk`
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        Reporter:  sgraf             |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  8.6.3
  (Hadrian)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by NeilMitchell):

 > I think the only solution is to have a way (e.g. a new GHC flag) to run
 dependency analysis on a single file, without transitive exploration of
 all its dependencies.

 That sounds reasonable. It would certainly be more robust than the
 strategy I describe. It won't help if you have deeply nested CPP includes
 (you'd still rescan them each time), but I suspect that's negligible for
 GHC.

 As you say, if that flag can take multiple files at once, you could batch
 it, which would be a good performance improvement.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16253#comment:14>
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