Sparse threads

[Lars Magne Ingebrigtsen <larsi@ifi.uio.no>]

I thought filling in "gaps" in threads (without reading further
headers) would be a) a major project and b) slow as hell, but it
turned out to be quite simple to do.  Just some References munging,
some sorting (since Message-IDs late in the References headers are
probably more reliable (with regards to what sequence articles have
been posted) than early Message-IDs), and some threading.  

Before:

---------------
   [  52: Egil Kvaleberg      ] Re: Redaktoransvar
       [  47: Erik Naggum         ] 
           [  25: Steinar Bang        ] 
       <  16: Gisle Hannemyr      > 
           [  14: Willy Verwoerd      ] 
---------------


After:

---------------
Q  [   0:                     ] Re: Redaktoransvar
       [  52: Egil Kvaleberg      ] 
           [  47: Erik Naggum         ] 
               [  25: Steinar Bang        ] 
Q      [   0:                     ] 
           [  16: Gisle Hannemyr      ] 
               [  14: Willy Verwoerd      ] 
---------------

The two articles that are marked with "Q" are the new "gaps" inserted
to fill out the thread.  They can't be selected.

On the other hand -- Gnus does know the Message-ID of the "gap"
articles, so it could just fire off a request-by-id command?  Yup, I
think I'll add that.

(14 features left on the todo list -- but they all require access to a
Real Computer to write, I think.  `open-network-stream', etc.  Curse
you, Windos '95!)

-- 
   Lars Magne Ingebrigtsen * larsi@ifi.uio.no
      (a red leaf that falls from the purple tree)