Get the Django AdminSite.index() method, from any URL in the admin, in a template tag... hmm.

templatetag.py

# there must be a better way :|
current_view = resolve(request.path)
root_url = reverse('%s:index' % current_view.app_name)
index_view = resolve(root_url)

# getting the actual AdminSite instance.
# This works on Python 2.
adminsite = index_view.func.func_closure[0].cell_contents
# this works on Python 2 and 3, because Python 3 seems to lack
# func_closure, and Python 2/3 have different ordering for the 
# cells in __closure__ ...
# SIGH.
try:
    adminsite = next(x.cell_contents for x in index_view.func.__closure__
                     if isinstance(x.cell_contents, AdminSite))
except StopIteration as e:
    adminsite = None