[MERGE][PING] Add --revision option to "update"

[Matthieu Moy]

Hi,

Just pinging 'cause this seems to have got lost (BTW, let me know if
you find those ping's annoying or useless):

http://www-verimag.imag.fr/~moy/bzr/bzr/bzr.update-r/

This adds a -r option to update, so that one can go back to a past
revision (or update to a future revision which is not the head of the
branch) while keeping the local changes.

It fixes https://launchpad.net/products/bzr/+bug/45719

-- 
Matthieu