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

[MacPorts]

#51310: ImageMagick: update to 7.x
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  Reporter:  mopihopi     |      Owner:  ryandesign
      Type:  update       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  ImageMagick  |
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Comment (by joostdekeijzer):

 Replying to [comment:17 ryandesign]:
 > The process to do that would be:
 > * Make the ImageMagick6 and ImageMagick7 ports, making sure the files
 get installed to different locations so that the two ports do not conflict
 > * Modify all ports that declare a dependency on ImageMagick so that they
 depend on ImageMagick6 instead, and modify each port's build system so
 that it knows how to find the ImageMagick6 files at their new locations,
 and increase the ports' revisions
 > * Keep an empty ImageMagick port for 1 year that is `replaced_by
 ImageMagick6` (using the obsolete-1.0 portgroup) to help users upgrade

 I've done some of the above, see https://github.com/joostdekeijzer
 /macports-ports/tree/ImageMagick-7/graphics

 * I've created a ImageMagick-6 and ImageMagick-7 port.
 * ImageMagick (itself) is set obsolete
 * The 6 and 7 ports install files in their own directories including the
 pkgconfig files so no conflicts can occur.

 I'ts possible to instruct ports that depend on ImageMagick pkgconfig files
 to instruct them to search in the ImageMagick-6 location, I've found this
 done for other ports and dependencies in MacPorts.

 @ryandesign and others: is this the route to take? I can try and find some
 time to change all the dependend ports.

 Maybe need some help with changing those portfiles as I'm not very fluent
 with all the build systems...

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Ticket URL: <https://trac.macports.org/ticket/51310#comment:26>
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