[tor-bugs] #29548 [Core Tor/Tor]: Block back-merges of later release branches to earlier releases

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#29548: Block back-merges of later release branches to earlier releases
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     Reporter:  teor          |      Owner:  (none)
         Type:  enhancement   |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: unspecified
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  git-scripts
Actual Points:                |  Parent ID:
       Points:  1             |   Reviewer:
      Sponsor:                |
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 In our release meeting in Brussels, we talked about blocking back-merges,
 where a merge is based on a later release branch, but it gets merged to an
 earlier branch:
 https://trac.torproject.org/projects/tor/wiki/org/meetings/2019BrusselsNetworkTeam/Notes/StableMaintainer#ActionItems

 Our merge workflow is typically:
 * base the bugfix branch on the maint branch for the earliest possible
 backport release
 * merge the bugfix branch to master (or alpha and master)
 * test for a while
 * merge the bugfix branch to an earlier release, then merge forward to
 master
 * merge maint-* into release-* for each release series

 So I'm not sure exactly how we can limit ourselves to just these merges.
 Here are some ideas:
 * Count the commits, and put a limit on the number of commits
 * Keep an ordered list of releases, and check that:
   * maint: merged branches are based on this maint release, or an earlier
 maint release
   * release: merged branches are based on the same maint release
 * Is there some neat trick that I'm missing?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29548>
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