[MacPorts] #59834: Boost: refactor and enhance

[MacPorts]

#59834: Boost: refactor and enhance
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  Reporter:  michaelld    |      Owner:  mascguy
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  boost        |
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Comment (by cjones051073):

 Changing the version of boost the old port provides requires testing every
 port using it, which is a herculean task no one really wants to take on.
 The approach taken is that with the new isolated boost ports, and the new
 boost PG to help configure ports to use the isolated builds. This way
 ports can be migrated to one of the boost versions currently offered, 1.69
 1.71 or 1.76. If there is a pressing reason for more versions they of
 course could be added.

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Ticket URL: <https://trac.macports.org/ticket/59834#comment:42>
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