[GHC] #8251: Validate submodule references during pre-receive hook

[GHC]

#8251: Validate submodule references during pre-receive hook
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        Reporter:  hvr               |            Owner:  hvr
            Type:  task              |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  None              |          Version:  7.6.3
      Resolution:                    |         Keywords:  admin git
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by hvr):

 Moreover, when adding a new submodule ref to a repository hosted at
 `git.haskell.org` another hook script could add a hidden ref or a
 [https://www.kernel.org/pub/software/scm/git/docs/git-notes.html Git note]
 to the referenced commit, effectively providing a back-ref, and ensuring
 the commit doesn't become dangling and subsequently garbage collected.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8251#comment:1>
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