Fix to fallback of thread by subject

[Stuartd]

The existing code in HyperDatabase.py looks like it
was intending to fallback to threading by subject if
the In-Reply-To and References headers were missing.

However the implementation it is broken, apparently
an incomplete port of some other module.

This patch fixes the set_location() method, and
getOldestArticle methods to allow subject threading
to once again work.

Note: pipermail.py has an unused database class which
also implements broken versions of these methods. This
patch does not fix those because they were unused.

[http://sourceforge.net/tracker/index.php?func=detail&aid=509269&group_id=103&atid=300103]

[Thomas Wouters (thomas)]

This patch looks like it still applies, but just looking at
this code makes my hea d go *splat*. Can you confirm that
this is still an issue for Mailman 2.1, and this is still
the correct fix ?

[Jean.c.h (slug71)]

Marked this bug as 'Invalid' due to its age and nothing further has been added in a long time. New versions have been released since as well as some underlying stuff in the OS platform itself.

If this bug still affects then please change status back to 'Confirmed'.

[Richard Tew (richard-m-tew)]

Oops

[Mark Sapiro (msapiro)]

This bug is still valid, but the patch is incomplete at best.

Preliminary testing shows that with the patch, rebuilding the archive with bin/arch --wipe works generally as expected, but individual posts without In-Reply-To: headers are still not threaded by Subject if the list has a subject_prefix. This appears to be the case whether or not the prefix is included in the reply as sent. The posts are unthreaded in the archive until the archive is rebuilt with bin/arch --wipe.

[Mark Sapiro (msapiro)]

Fixed at rev 1220 on the 2.1 branch and rev 1093 on the 2.2 branch.

The fix is probably still incomplete. I think there will still be issues when long subjects are folded and unfolded. A possible fix is to remove all white space from 'stripped' subjects or maybe replace all runs of whitespace with a single space.