[GHC] #5442: ghc-pkg unregister --user/--global/--package-conf not normative

[GHC]

#5442: ghc-pkg unregister --user/--global/--package-conf not normative
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              Reporter:  guest       |             Owner:  ezyang
                  Type:  bug         |            Status:  patch
              Priority:  normal      |         Milestone:  7.10.1
             Component:  ghc-pkg     |           Version:  7.2.1
            Resolution:              |          Keywords:
Differential Revisions:  Phab:D84    |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  Other
  Unknown/Multiple                   |         Test Case:
            Difficulty:  Unknown     |          Blocking:
            Blocked By:              |
       Related Tickets:              |
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Comment (by Edward Z. Yang <ezyang@…>):

 In [changeset:"d7c807f7975c13444e1ce79e4c36dd802321cf40/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="d7c807f7975c13444e1ce79e4c36dd802321cf40"
 [ghc-pkg] Fix #5442 by using the flag db stack to modify packages.

 Summary:
 Previously, the full database stack was used for ghc-pkg to
 modify packages, which meant that commands like
 'ghc-pkg unregister --user' worked the same as 'ghc-pkg unregister'.
 Since package modification is a "read and write" operation, we
 should use the flag db stack (which is currently used for reads)
 to determine which database to update.

 There is also a new flag --user-package-db, which lets you explicitly
 set the user database (as seen by --user).  This was mostly added
 to aid in testing, but could be useful for end users as well.

 Signed-off-by: Edward Z. Yang <ezyang at cs.stanford.edu>

 Test Plan: validate

 Reviewers: simonmar, hvr, austin

 Subscribers: simonmar, relrod, carter

 Differential Revision: https://phabricator.haskell.org/D84
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5442#comment:10>
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