[MacPorts] #51310: ImageMagick: update to 7.x

[MacPorts]

#51310: ImageMagick: update to 7.x
--------------------------+------------------------
  Reporter:  mopihopi     |      Owner:  ryandesign
      Type:  update       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  ImageMagick  |
--------------------------+------------------------

Comment (by diekhans):

 PR 21692 does not allow imagemagick 6 and 7 to co-exist.  There are
 multiple install conflicts.  I will document these to the PR.

 Given the requirement that "A commit affects one port," I don't see how
 this approach will work.  Having imagemagick 6 and 7 coexist and both look
 like a standard install seems not possible.   Some kind of incremental
 approach, as suggested by kencu, seems necessary.

-- 
Ticket URL: <https://trac.macports.org/ticket/51310#comment:82>
MacPorts <https://www.macports.org/>
Ports system for macOS