[MacPorts] #51092: Add search key and pseudo-port selector for port groups

[MacPorts]

#51092: Add search key and pseudo-port selector for port groups
-------------------------+----------------------
 Reporter:  raimue@…     |      Owner:  raimue@…
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  base         |    Version:
 Keywords:               |       Port:
-------------------------+----------------------
 Similar to other field selectors it should be possible to select ports by
 which port groups they require. This should work both in search

 Example Portfile:

 {{{
 PortGroup foo 1.0
 PortGroup bar 1.5

 name      blah
 ...
 }}}

 Expected commands and output:

 {{{
 $ port echo portgroup:foo
 blah
 $ port echo groups:bar
 blah
 $ port search --groups foo
 blah @...
    ...
 $ port info --groups blah
 groups: foo 1.0, bar 1.5
 }}}

 The field `PortInfo(portgroups)` already exists. It is just not written
 into the `PortIndex`. It is currently a nested list of port groups and the
 corresponding version: `{{foo 1.0} {bar 1.5}}`.

-- 
Ticket URL: <https://trac.macports.org/ticket/51092>
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