[MacPorts] #47218: protobuf3-cpp: update to 3.0.0-alpha-2

[MacPorts]

#47218: protobuf3-cpp: update to 3.0.0-alpha-2
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  Reporter:  ryandesign@…   |      Owner:  blair@…
      Type:  update         |     Status:  new
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:  2.3.99
Resolution:                 |   Keywords:  haspatch
      Port:  protobuf3-cpp  |
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Comment (by blair@…):

 Thanks.

 I was using alpha1 because https://github.com/grpc/grpc uses alpha1 in its
 git submodule, although I may initially have a gRPC port just use the
 protobuf version that gRPC has for its submodule.

 I also dislike epoch, although I guess it's cleaner then all the
 real_version stuff I do.

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Ticket URL: <https://trac.macports.org/ticket/47218#comment:1>
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