def promote
db_id = extract_option("--db")
url = config_vars[db_id]
abort(" ! Usage: heroku pg:promote --db <DATABASE>") unless url
name = config_vars.reject { |(var, val)| var == "DATABASE_URL" }.invert[url] || "DATABASE_URL"
if db_id == "DATABASE_URL"
abort(" ! Promoting DATABASE_URL to DATABASE_URL has no effect.")
return
end
abort(" ! DATABASE_URL is already set to #{name}.") if url == config_vars["DATABASE_URL"]
display "Setting config variable DATABASE_URL to #{name}", false
return unless confirm_command
display "... "
heroku.add_config_vars(app, {"DATABASE_URL" => url})
display "done"
display "DATABASE_URL (#{name}) => #{url}"
display ""
end