I was aiming to run with empty DATABASE_URL and for the database `psql` connects to without any arguments. I was also going for unix sockets instead of tcp and for that the hostname needs to be empty. I don't really care about the database name. Having it named $USER works for me since I save a few characters every time I run `psql`. We can easily make it similar to the testing database (`DATABASE_URL=dbname=gittip`) if that would make any difference.