[tor-bugs] #18857 [Core Tor/Tor]: Add a soft-deprecation mechanism for configuration options

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#18857: Add a soft-deprecation mechanism for configuration options
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     Reporter:  nickm         |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.2.???
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  029-proposed
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 I'd like to have a way to flag configuration options as "dubious but still
 supported", and warn users that those options might go away completely
 unless they explain to us that no, somebody is still using them.

 There's a ticket about killing off old options that nobody is using (can't
 find it, though), and I've started nominating options for my own person
 sadness at
 https://docs.google.com/spreadsheets/d/1Np1vBm0jSvUqxwaQdhkqDmYWxe4E3RO0R5RoRMtpkQQ/edit?usp=sharing
 .

 But unless we have a way to mark an option as "warn if set", then we won't
 have a nice way to do transitions here.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18857>
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