[MacPorts] #59538: github portgroup doesn't work with default master_sites from other portgroups

[MacPorts]

#59538: github portgroup doesn't work with default master_sites from other
portgroups
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  Reporter:  jmroot  |      Owner:  (none)
      Type:  defect  |     Status:  new
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:
      Port:          |
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Comment (by ryandesign):

 It sets a default for master_sites that is appropriate for downloading the
 type of GitHub file specified in github.tarball_from. Ports can and do
 override master_sites. The portgroup used to set master_sites, but it was
 [changeset:62d22c69d893460a16aa1c1dc334d12619bf641d/macports-ports changed
 8.5 years ago] to only set a default because that made some things easier.

 The portgroup is kind of terrible at this point. I tried maybe a year ago
 to spec out a new github-2.0 portgroup to fix all of its problems,
 including wanting to be able to download any number of files from any
 number of different GitHub projects (see for example the MoltenVK port),
 but I didn't reach a satisfactory conclusion; I couldn't decide how
 everything should work.

 We should add support to MacPorts base for downloading from different
 types of GitHub files, just as base already has support for downloading
 from SourceForge. The new portgroup could then use that.

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Ticket URL: <https://trac.macports.org/ticket/59538#comment:3>
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