The "loose" (Subject:-based) thread matching yields too many
hits for some common subjects (e.g. "[GIT] Networking" on LKML)
and causes thread skeletons to not show the current messages.
Favor strict matches in the query and only add loose matches
if there's space.
While working on this, I noticed the backwards --reindex walk
breaks `tid' on v1 repositories, at least. That bug was hidden
by the Subject: match logic and not discovered until now. It
will be fixed separately.
Reported-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>