I see the request has been accepted and the packages merged. But shouldn't pentadactyl-hg then resolve to pentadactyl-git? Currently it just gives a 404, so trying to update pentadactyl-hg with an AUR wrapper just gives "target not found".
I believe giving a 301 redirect to pentadactyl-git would be the Right Thing. AUR wrappers could then handle merged packages gracefully, including alerting the user about the merge.
AsmundEr  filed a request to merge pentadactyl-hg  into
Upstream pentadactyl recently switched from hg to git (when Google
Code was shut down). So I created a new pentadactyl-git package which
is identical to the current pentadactyl-hg (PKGBUILD was updated to
use git a few weeks ago). I am the maintainer for both packages.