formatter: put topic in templatespec tuple...
formatter: put topic in templatespec tuple
This will allow us to change the initial template reference depending on how
the template is looked up. For example,
-Tdefault => (ref='changeset', tmpl=None, mapfile='map-cmdline.default')
-T'{rev}' => (ref='', tmpl='{rev}', mapfile=None)
A literal template given by -T option will be stored as an unnamed template,
which will free up the template namespace so that we can load named templates
from [templates] section of user config.
