name change doesn't clear trunk_id+discussion

Can't reproduce this.  Let's get a concrete example or close it.

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The old example seemed okay, but i did a new one just to be sure. See above. --John Abbe

  --John Abbe.....Mon Dec 08 00:11:54 -0800 2008

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This was actually pretty easy. Simple test, simple unintrusive fix. The only part I'm a little concerned about is the migration, which relies on a find_by_sql. If there's a better way to do it I'm all ears.

  --Ethan McCutchen.....Fri Dec 19 11:36:55 -0800 2008