Revive commands.dispatch as a simple way to call hg from other pythons scripts. This was already used by hg-ssh and others and is really convenient if you just want a native equivalent of calling the command line version.

#!/bin/sh

hg init

echo "Is there an error message when trying to diff non-existing files?"
hg diff not found

echo "Is there an error message when trying to add non-existing files?"
hg add not found