In build upstream bare repo (webserver:/usr/local/src/web/example.com/www/), run:
	# git worktree add /srv/beta/example.com/www master
	# git worktree add /srv/prod/example.com/www release
	# git config receive.denyCurrentBranch updateInstead
	# chown -R root:srv .
	# chmod -R g+xwX .
and add your user (on the server) to the srv group.