It would be much simpler for users to maintain an installation of arcanist using macports. Naturally this requires 'releases' which phabricator doesn't have, but it would be easy enough to pick a git commit once every 3 months or so and 'release' a macport update.
Then for users, installing arcanist is reduced to
sudo port install arcanist
I'm not how "arc upgrade" helps here, since you still need to first install arcanist. Which goes something like this:
sudo port install php sudo port install git mkdir /opt/phabricator cd /opt/phabricator/ git clone https://github.com/phacility/libphutil.git git clone https://github.com/phacility/arcanist.git echo "PATH=$PATH:/opt/phabricator/arcanist/bin" >> ~/.profile
So it isn't hard, but a macport reduces that all to one command.
T4200 covers why this is not likely to be pursued for a long time. https://secure.phabricator.com/book/phabcontrib/article/feature_requests/ covers requesting features here in general.
Unfortunately, regardless of how "easy" a feature is to build, there is a real cost to support, documentation, and lifetime maintenance. As we're a very small team (3 people) we're very specific about what we decide to pull in and build. As far as I'm aware, there has been no other requests for this. T4200 covers where we want general feedback for what to support when we're at a point we feel it's worth the cost, happy to have your feedback there.
That makes sense. If I have the time I'll look at making a port myself. The nice thing about your "arc upgrade" command is that the macport itself need rarely be upgraded and that command executed as a normal part of the install.