Merged from trunk 11125:11139

   Merged from trunk 11125:11139

   | 11126   | Bug #199788 - Make repoman parse GLEP 56 USE flag            |
   | zmedico | descriptions from metadata.xml (in addition to               |
   |         | use.local.desc). Thanks to Doug Goldstein <cardoe@g.o> for   |
   |         | this patch.                                                  |

   | 11127   | Add a MergeListItem.statusMessage(msg) callback for          |
   | zmedico | displaying messages like "Building this" or "Installing      |
   |         | that". This delegates the resposibility of generating \r and |
   |         | \n control characters, to guarantee that lines are created   |
   |         | or erased when necessary and appropriate. TODO: Make         |
   |         | JobStatusDisplay display the output.                         |

   | 11128   | Add support to JobStatusDisplay() to update the current line |
   | zmedico | on the terminal, which in the future can be used to erase    |
   |         | the line and update it with new information such as the      |
   |         | latest load average measurement. This uses curses to obtain  |
   |         | the simple control codes that are needed, and has fallback   |
   |         | codes in case the curses module is unavailable or raises an  |
   |         | error. When stdout is not a tty then the line erasing        |
   |         | behavior is automatically disabled and display updates are   |
   |         | simply show on a new line.                                   |

   | 11129   | When JobStatusDisplay.displayMessage() is called while the   |
   | zmedico | status is currently displayed, call display() after showing  |
   |         | the given message.                                           |

   | 11130   | Make all poll() calls pass through PollScheduler._poll().    |
   | zmedico |                                                              |

   | 11131   | Add a hook in Scheduler._poll() that updates the display     |
   | zmedico | once every 2 seconds if stdout is a tty, so that the load    |
   |         | average numbers are always current.                          |

   | 11132   | Display "Verifying ebuild manifests" and "Starting parallel  |
   | zmedico | fetch" via the status display instead of directly to stdout. |

   | 11133   | Add a Scheduler._background_mode() method to control         |
   | zmedico | background mode, and trigger it if either --quiet is enabled |
   |         | or --jobs > 1.                                               |

   | 11134   | Fix typos.                                                   |
   | zmedico |                                                              |

   | 11135   | * Call self._schedule() from inside Scheduler._poll(). This  |
   | zmedico | ensures that new jobs can scheduled as soon a the load       |
   |         | average is low enough, and one of the running jobs doesn't   |
   |         | have to complete for _schedule() to get called. * Cache the  |
   |         | result of _background_mode() so it doesn't have to be called |
   |         | inside _schedule(), since this method is called a lot more   |
   |         | often now. * Move background related state adjustments into  |
   |         | _background_mode(). * Call _status_display.display()         |
   |         | unconditionally inside _schedule_tasks(), since we want to   |
   |         | update the display to show current load average even if no   |
   |         | new jobs are added.                                          |

   | 11136   | Fix JobStatusDisplay._init_term() to supply default codes in |
   | zmedico | cases when curses.tigetstr() returns None.                   |

   | 11137   | Instead of calling _background_mode(), use the cached        |
   | zmedico | result.                                                      |

   | 11138   | Bug #231464 - Replace erroneous "return" statement in        |
   | zmedico | elog_process() with a continue statement. Thanks to TGL for  |
   |         | this patch.                                                  |

   | 11139   | When Scheduler._choose_pkg() is unable to find a package,    |
   | zmedico | memoize the result until at least one of the existing jobs   |
   |         | completes.                                                   |

svn path=/main/branches/prefix/; revision=11148