[MacPorts] #71748: boost PG: update default version to 1.87

[MacPorts]

#71748: boost PG: update default version to 1.87
-------------------------+--------------------
  Reporter:  mohd-akram  |      Owner:  (none)
      Type:  update      |     Status:  new
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:
      Port:  boost       |
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Comment (by ryandesign):

 If you were to change the default version in the portgroup, that would
 change the dependencies of the ports that use the portgroup and don't
 specify a boost version. That wouldn't be [ReproducibleBuilds
 reproducible]—people who installed the port before, as well as people
 installing the port now and receiving a binary from us, would be using the
 old default boost and people building the port from source now would get
 the new default boost. At best, that would be inconsistent. To address the
 inconsistency, you would have to identify and revbump those ports to
 rebuild them. It's likely, though, that the software simply would fail to
 build with the newer boost.

 Boost is notoriously not backwards-compatible. That is why the boost
 portgroup was created, and separate versioned boost ports were created to
 replace the old single boost port: so that each port that uses boost can
 specify which version it needs.

 Removing the default version, and requiring ports to specify the version,
 is an excellent idea which should have been implemented in the portgroup
 from the beginning.

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Ticket URL: <https://trac.macports.org/ticket/71748#comment:3>
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