Merged from trunk -r12347:12352

   Merged from trunk -r12347:12352

   | 12348   | Bug #252572 - Fix a loop condition inside                    |
   | zmedico | depgraph._serialize_tasks() which can cause an infinite loop |
   |         | that's triggered by unresolvable blockers.                   |

   | 12349   | Fix loop logic some more for bug #252572.                    |
   | zmedico |                                                              |

   | 12350   | Bail out earlier if the file name argument doesn't end with  |
   | zmedico | '.ebuild'. Thanks to Diego 'Flameeyes' Pettenò for          |
   |         | reporting.                                                   |

   | 12351   | Bug #252562 - Show --onlydeps in short --help output.        |
   | zmedico |                                                              |

   | 12352   | Revert r12348 since it's not really needed and the previous  |
   | zmedico | version is more efficient.                                   |

svn path=/main/branches/prefix/; revision=12390