Even though the paragraph before this one is pretty clear that
topics are first merged to 'master' and then to 'maint', it was
misleading to say 'maint' is merged to 'master' to propagate fixes
forward, as most of the time, such an upmerge is a noop because
topics merged to 'maint' are usually merged to 'master' already.

These up-merges are done primarily to make sure that the tip of
'master' has updated release notes from all the maintenance tracks,
so be explicit about that to avoid confusion.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

A new topic that is still not ready for 'pu' which uses a topic in
flight appear in the description of the latter as "used by", even
though it does not appear in the report anywhere else.  Leave a note
to the place where this bug happens, as I do not have time to fix it
right now.