[MacPorts] #38508: RFE: add version number support to `platforms` field in portfiles

[MacPorts]

#38508: RFE: add version number support to `platforms` field in portfiles
-------------------------+--------------------------------
 Reporter:  egall@…      |      Owner:  macports-tickets@…
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  base         |    Version:  2.1.3
 Keywords:               |       Port:
-------------------------+--------------------------------
 Thought of this is #38506; not sure if there's already a ticket open for
 it...

 Anyway, currently, if a port is incompatible with a certain OS version,
 the portfile author has to write something like this:
 {{{
 pre-fetch {
     if {${os.platform} == "darwin" && ${os.major} < 9} {
         ui_error "${name} is only supported on OS X 10.5 Leopard or
 later."
         return -code error "unsupported platform version"
     }
 }
 }}}
 It'd be much easier to just be able to write something like`platforms
 darwin 9+` or something like that instead.

-- 
Ticket URL: <https://trac.macports.org/ticket/38508>
MacPorts <http://www.macports.org/>
Ports system for OS X