[MacPorts] #18794: Add conflicts option for Portfiles

[MacPorts]

#18794: Add conflicts option for Portfiles
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  Reporter:  blb@…             |       Owner:  macports-tickets@…                   
      Type:  enhancement       |      Status:  closed                               
  Priority:  Normal            |   Milestone:  MacPorts 1.8.0                       
 Component:  base              |     Version:  1.7.0                                
Resolution:  fixed             |    Keywords:                                       
      Port:                    |  
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Changes (by jmr@…):

 * cc: jmr@… (added)
  * status:  new => closed
  * resolution:  => fixed
  * milestone:  MacPorts Future => MacPorts 1.8.0


Comment:

 Committed a modified version in r51525. Most importantly, the check is
 done in mportdepends, so for `port install`, the conflict is detected
 before anything gets installed. Upgrade (as usual) presents its own
 special challenge, since it installs one port at a time.

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Ticket URL: <http://trac.macports.org/ticket/18794#comment:1>
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