[MacPorts] #55673: destroot.keepdirs should behave better if specified path is not in destroot

[MacPorts]

#55673: destroot.keepdirs should behave better if specified path is not in destroot
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  Reporter:  ryandesign  |      Owner:  (none)
      Type:  defect      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  base        |    Version:  2.4.2
Resolution:              |   Keywords:
      Port:              |
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Comment (by jmroot):

 Replying to [ticket:55673 ryandesign]:
 > I'm still unclear why we went back to `.turd` files. James, do you
 remember?

 Installed directories are not recorded in the registry, only files (one
 reason being that multiple ports may cause a given directory to be
 created). So you need a way to both ensure that otherwise empty
 directories that need to keep existing are not deleted when uninstalling
 other ports that had files in those directories, and that those
 directories are deleted when all ports that need them are uninstalled.

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Ticket URL: <https://trac.macports.org/ticket/55673#comment:1>
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